Search

A vegetated channel refers to a form of infrastructure that aims to mitigate stormwater runoff through the utilization of either natural or constructed systems that replicate the behavior observed in natural environments. The condition of the vegetated channel has the potential to influence the hydraulic behavior of the channel. The regulation of stormwater quantity in the management of drainage systems is influenced by the characteristics of the vegetated channel. Field data was gathered from a channel located in the parking lot of the Faculty of Civil Engineering and Built Environment at the University Tun Hussien Onn Malaysia (UTHM) campus. The purpose of this data collection was to assess the influence of various sectional circumstances on the velocity profile. The measurement of stream flow velocity is conducted by the utilization of current meter equipment during field investigation. The Manning's coefficient for each section was analyzed to assess the impact of variations in this parameter on the flow rate of the channel. In accordance with the results obtained, the coefficient value of Manning's ranged from 0.160 to 0.826. The velocity of flow in the vegetated channel ranged from 0.003 m/s to 0.010 m/s. In the interim, the flow discharge magnitude for the channel exhibits variability within the range of 0.0005 m3/s to 0.002 m3/s. This study examines the impact of bed surface condition, channel slope, and Manning's coefficient on flow rate. Therefore, the flow rate and Manning's coefficient were found to be impacted by both the bed condition and the slope of the channel.

A vegetated channel refers to a form of infrastructure that aims to mitigate stormwater runoff through the utilization of either natural or constructed systems that replicate the behavior observed in natural environments. The condition of the vegetated channel has the potential to influence the hydraulic behavior of the channel. The regulation of stormwater quantity in the management of drainage systems is influenced by the characteristics of the vegetated channel. Field data was gathered from a channel located in the parking lot of the Faculty of Civil Engineering and Built Environment at the University Tun Hussien Onn Malaysia (UTHM) campus. The purpose of this data collection was to assess the influence of various sectional circumstances on the velocity profile. The measurement of stream flow velocity is conducted by the utilization of current meter equipment during field investigation. The Manning's coefficient for each section was analyzed to assess the impact of variations in this parameter on the flow rate of the channel. In accordance with the results obtained, the coefficient value of Manning's ranged from 0.160 to 0.826. The velocity of flow in the vegetated channel ranged from 0.003 m/s to 0.010 m/s. In the interim, the flow discharge magnitude for the channel exhibits variability within the range of 0.0005 m3/s to 0.002 m3/s. This study examines the impact of bed surface condition, channel slope, and Manning's coefficient on flow rate. Therefore, the flow rate and Manning's coefficient were found to be impacted by both the bed condition and the slope of the channel.

Wall shear stress (WSS)—a key regulator of endothelial function—is commonly estimated in vivo using simplified mathematical models based on Poiseuille's flow, assuming a quasi-steady parabolic velocity distribution, despite evidence that more rapidly time-varying, pulsatile blood flow during each cardiac cycle modulates flow-mediated dilation (FMD) in large arteries of healthy subjects. More exact and accurate models based on the well-established Womersley solution for rapidly changing blood flow have not been adopted clinically, potentially because the Womersley solution relies on the local pressure gradient, which is difficult to measure non-invasively. We have developed an open-source method for automatic reconstruction of unsteady, Womersley-derived velocity profiles, and WSS in conduit arteries. The proposed method (available online at https://doi.org/10.5281/zenodo.7576408) requires only the time-averaged diameter of the vessel and time-varying velocity data available from non-invasive imaging such as Doppler ultrasound. Validation of the method with subject-specific computational fluid dynamics and application to synthetic velocity waveforms in the common carotid, brachial, and femoral arteries reveals that the Poiseuille solution underestimates peak WSS 38.5%–55.1% during the acceleration and deceleration phases of systole and underestimates or neglects retrograde WSS. Following evidence that oscillatory shear significantly augments vasodilator production, it is plausible that mischaracterization of the shear stimulus by assuming parabolic flow leads to systematic underestimates of important biological effects of time-varying blood velocity in conduit arteries.

Wall shear stress (WSS)—a key regulator of endothelial function—is commonly estimated in vivo using simplified mathematical models based on Poiseuille's flow, assuming a quasi-steady parabolic velocity distribution, despite evidence that more rapidly time-varying, pulsatile blood flow during each cardiac cycle modulates flow-mediated dilation (FMD) in large arteries of healthy subjects. More exact and accurate models based on the well-established Womersley solution for rapidly changing blood flow have not been adopted clinically, potentially because the Womersley solution relies on the local pressure gradient, which is difficult to measure non-invasively. We have developed an open-source method for automatic reconstruction of unsteady, Womersley-derived velocity profiles, and WSS in conduit arteries. The proposed method (available online at https://doi.org/10.5281/zenodo.7576408) requires only the time-averaged diameter of the vessel and time-varying velocity data available from non-invasive imaging such as Doppler ultrasound. Validation of the method with subject-specific computational fluid dynamics and application to synthetic velocity waveforms in the common carotid, brachial, and femoral arteries reveals that the Poiseuille solution underestimates peak WSS 38.5%–55.1% during the acceleration and deceleration phases of systole and underestimates or neglects retrograde WSS. Following evidence that oscillatory shear significantly augments vasodilator production, it is plausible that mischaracterization of the shear stimulus by assuming parabolic flow leads to systematic underestimates of important biological effects of time-varying blood velocity in conduit arteries.

A laminar boundary jet adjacent to a vertical sidewall of a rotating circular cylinder was studied experimentally. The boundary jet was produced by differential rotation of a ring-shaped plate along the periphery of the top surface of the working fluid. The velocity field of the resulting boundary jet was observed by a pH-indiator method with special interest in the case when the with of the driving ring was O (E^1/4 (Eis the Ekman number). It was demonstrated that the azimuthal velocity has an appreciable vertical shear and that the vertical velocity in the boundary jet is of order £114. The vertically averaged azimuthal velocity profile was compared with an empirical formula which is a modified version of the theoretical solution given by Kimura (1976)

Wall shear stress (WSS)—a key regulator of endothelial function—is commonly estimated in vivo using simplified mathematical models based on Poiseuille's flow, assuming a quasi-steady parabolic velocity distribution, despite evidence that more rapidly time-varying, pulsatile blood flow during each cardiac cycle modulates flow-mediated dilation (FMD) in large arteries of healthy subjects. More exact and accurate models based on the well-established Womersley solution for rapidly changing blood flow have not been adopted clinically, potentially because the Womersley solution relies on the local pressure gradient, which is difficult to measure non-invasively. We have developed an open-source method for automatic reconstruction of unsteady, Womersley-derived velocity profiles, and WSS in conduit arteries. The proposed method (available online at https://doi.org/10.5281/zenodo.7576408) requires only the time-averaged diameter of the vessel and time-varying velocity data available from non-invasive imaging such as Doppler ultrasound. Validation of the method with subject-specific computational fluid dynamics and application to synthetic velocity waveforms in the common carotid, brachial, and femoral arteries reveals that the Poiseuille solution underestimates peak WSS 38.5%–55.1% during the acceleration and deceleration phases of systole and underestimates or neglects retrograde WSS. Following evidence that oscillatory shear significantly augments vasodilator production, it is plausible that mischaracterization of the shear stimulus by assuming parabolic flow leads to systematic underestimates of important biological effects of time-varying blood velocity in conduit arteries.

A laminar boundary jet adjacent to a vertical sidewall of a rotating circular cylinder was studied experimentally. The boundary jet was produced by differential rotation of a ring-shaped plate along the periphery of the top surface of the working fluid. The velocity field of the resulting boundary jet was observed by a pH-indiator method with special interest in the case when the with of the driving ring was O (E^1/4 (Eis the Ekman number). It was demonstrated that the azimuthal velocity has an appreciable vertical shear and that the vertical velocity in the boundary jet is of order £114. The vertically averaged azimuthal velocity profile was compared with an empirical formula which is a modified version of the theoretical solution given by Kimura (1976)

Wall shear stress (WSS)—a key regulator of endothelial function—is commonly estimated in vivo using simplified mathematical models based on Poiseuille's flow, assuming a quasi-steady parabolic velocity distribution, despite evidence that more rapidly time-varying, pulsatile blood flow during each cardiac cycle modulates flow-mediated dilation (FMD) in large arteries of healthy subjects. More exact and accurate models based on the well-established Womersley solution for rapidly changing blood flow have not been adopted clinically, potentially because the Womersley solution relies on the local pressure gradient, which is difficult to measure non-invasively. We have developed an open-source method for automatic reconstruction of unsteady, Womersley-derived velocity profiles, and WSS in conduit arteries. The proposed method (available online at https://doi.org/10.5281/zenodo.7576408) requires only the time-averaged diameter of the vessel and time-varying velocity data available from non-invasive imaging such as Doppler ultrasound. Validation of the method with subject-specific computational fluid dynamics and application to synthetic velocity waveforms in the common carotid, brachial, and femoral arteries reveals that the Poiseuille solution underestimates peak WSS 38.5%–55.1% during the acceleration and deceleration phases of systole and underestimates or neglects retrograde WSS. Following evidence that oscillatory shear significantly augments vasodilator production, it is plausible that mischaracterization of the shear stimulus by assuming parabolic flow leads to systematic underestimates of important biological effects of time-varying blood velocity in conduit arteries.

The article deals with the theoretical description and experimental study of the hydrodynamic and heat transfer properties regarding the operation of multistage gravitational devices of the fluidized bed with inclined perforated shelves. The peculiarities of the work and the implementation field of the multistage shelf units are described. A theoretical model to define the solubilizer’s velocity above the perforation holes, in the above-shelf space of the device and in the outloading gap, as well as the residence time of the dispersed phase at the stage (perforated shelf contact) of the device is presented. The results of experimental studies regarding the influence, made by the structural parameters of the perforated shelf contacts, on the distribution pattern of single-phase and gas-dispersed flows in the workspace of the device, on the intensity of interphase heat transfer are presented. The conditions to create active hydrodynamic operating modes of multistage gravitational shelf devices, which provide higher efficiency of heat-mass transfer processes, and with lower gas consumption and hydraulic resistance compared to typical fluidized bed devices, are proved. Peculiarities regarding the implementation of heat-mass transfer processes in multistage devices are described using heat treatment and drying processes as examples., Článek se zabývá teoretickým popisem a experimentálním studiem hydrodynamických a tepelných přenosových vlastností týkajících se provozu vícestupňových gravitačních zařízení s fluidním lůžkem se šikmými perforovanými policemi. Zvláštnosti týkající se implementace procesů přenosu teplých materiálů ve vícestupňových zařízeních jsou popsány pomocí příkladů procesů tepelného zpracování a sušení.

[ES] La realización de ensayos en túneles de viento puede, en ciertos casos, dar lugar a simulaciones inexactas, ya que el flujo que estos reproducen tiene un perfil de velocidades determinado. Este perfil de velocidades puede diferir con el que afectará realmente al componente estudiado, por ejemplo, si este se encuentra en la realidad dentro de un motor. El uso de una pantalla de distorsión permite generar un perfil de velocidades que simule, en ensayos en túneles de viento, unas condiciones del flujo más ajustadas al caso real. En este trabajo se estudia, mediante la dinámica de fluidos computacional (CFD), la alteración del flujo provocada al introducir una pantalla de distorsión en un túnel de viento, es decir, la variación de las velocidades, presiones, la generación de turbulencia, etc. Esta pantalla de distorsión ha sido generada con el objetivo de replicar un cierto perfil de velocidades deseado para un ensayo en túnel de viento. Se realiza, además, una validación del modelo CFD mediante resultados experimentales extraídos de la implementación de la pantalla física en un túnel de viento. Finalmente, se realiza una comparación del perfil de velocidades obtenido tanto de forma numérica como experimental con el perfil de velocidades deseado., [EN] Carrying out tests in wind tunnels can lead, in certain cases, to inaccurate simulations, since the flow they reproduce has a specific velocity profile. This speed profile may differ from the one that will affect the component studied under real circumstances, for instance, if it is actually located inside an engine. The use of a distortion screen makes it possible to generate a velocity profile that simulates, in tests in wind tunnels, certain flow conditions that are more adjusted to the real case. In this work, through computational fluid dynamics (CFD), the alteration of the flow caused by a distortion screen in a wind tunnel is studied, which implies the variation of speeds, pressures, generation of turbulence, etc. This distortion screen has been engineered in order to replicate a certain velocity profile desired for a wind tunnel test. Furthermore, a validation of the CFD model is carried out by means of experimental results extracted from the implementation of the physical screen in a wind tunnel. Finally, a comparison between both numerically and experimentally obtained velocity profiles and the desired velocity profile is done.

[ES] La realización de ensayos en túneles de viento puede, en ciertos casos, dar lugar a simulaciones inexactas, ya que el flujo que estos reproducen tiene un perfil de velocidades determinado. Este perfil de velocidades puede diferir con el que afectará realmente al componente estudiado, por ejemplo, si este se encuentra en la realidad dentro de un motor. El uso de una pantalla de distorsión permite generar un perfil de velocidades que simule, en ensayos en túneles de viento, unas condiciones del flujo más ajustadas al caso real. En este trabajo se estudia, mediante la dinámica de fluidos computacional (CFD), la alteración del flujo provocada al introducir una pantalla de distorsión en un túnel de viento, es decir, la variación de las velocidades, presiones, la generación de turbulencia, etc. Esta pantalla de distorsión ha sido generada con el objetivo de replicar un cierto perfil de velocidades deseado para un ensayo en túnel de viento. Se realiza, además, una validación del modelo CFD mediante resultados experimentales extraídos de la implementación de la pantalla física en un túnel de viento. Finalmente, se realiza una comparación del perfil de velocidades obtenido tanto de forma numérica como experimental con el perfil de velocidades deseado., [EN] Carrying out tests in wind tunnels can lead, in certain cases, to inaccurate simulations, since the flow they reproduce has a specific velocity profile. This speed profile may differ from the one that will affect the component studied under real circumstances, for instance, if it is actually located inside an engine. The use of a distortion screen makes it possible to generate a velocity profile that simulates, in tests in wind tunnels, certain flow conditions that are more adjusted to the real case. In this work, through computational fluid dynamics (CFD), the alteration of the flow caused by a distortion screen in a wind tunnel is studied, which implies the variation of speeds, pressures, generation of turbulence, etc. This distortion screen has been engineered in order to replicate a certain velocity profile desired for a wind tunnel test. Furthermore, a validation of the CFD model is carried out by means of experimental results extracted from the implementation of the physical screen in a wind tunnel. Finally, a comparison between both numerically and experimentally obtained velocity profiles and the desired velocity profile is done.

[ES] La realización de ensayos en túneles de viento puede, en ciertos casos, dar lugar a simulaciones inexactas, ya que el flujo que estos reproducen tiene un perfil de velocidades determinado. Este perfil de velocidades puede diferir con el que afectará realmente al componente estudiado, por ejemplo, si este se encuentra en la realidad dentro de un motor. El uso de una pantalla de distorsión permite generar un perfil de velocidades que simule, en ensayos en túneles de viento, unas condiciones del flujo más ajustadas al caso real. En este trabajo se estudia, mediante la dinámica de fluidos computacional (CFD), la alteración del flujo provocada al introducir una pantalla de distorsión en un túnel de viento, es decir, la variación de las velocidades, presiones, la generación de turbulencia, etc. Esta pantalla de distorsión ha sido generada con el objetivo de replicar un cierto perfil de velocidades deseado para un ensayo en túnel de viento. Se realiza, además, una validación del modelo CFD mediante resultados experimentales extraídos de la implementación de la pantalla física en un túnel de viento. Finalmente, se realiza una comparación del perfil de velocidades obtenido tanto de forma numérica como experimental con el perfil de velocidades deseado., [EN] Carrying out tests in wind tunnels can lead, in certain cases, to inaccurate simulations, since the flow they reproduce has a specific velocity profile. This speed profile may differ from the one that will affect the component studied under real circumstances, for instance, if it is actually located inside an engine. The use of a distortion screen makes it possible to generate a velocity profile that simulates, in tests in wind tunnels, certain flow conditions that are more adjusted to the real case. In this work, through computational fluid dynamics (CFD), the alteration of the flow caused by a distortion screen in a wind tunnel is studied, which implies the variation of speeds, pressures, generation of turbulence, etc. This distortion screen has been engineered in order to replicate a certain velocity profile desired for a wind tunnel test. Furthermore, a validation of the CFD model is carried out by means of experimental results extracted from the implementation of the physical screen in a wind tunnel. Finally, a comparison between both numerically and experimentally obtained velocity profiles and the desired velocity profile is done.

Kinematics is a key component of a landslide hazard because landslides moving at similar rates can affect structures or collapse differently depending on their mechanisms. While a complete definition of landslide kinematics requires integrating surface and subsurface site investigation data, its practical estimate is usually based on 2D profiles of surface slope displacements. These can be now measured accurately using Persistent Scatterer InSAR (PSI), which exploits open access satellite imagery. Although 2D profiles of kinematic quantities are easy to retrieve, the efficacy of possible descriptors and extraction strategies has not been systematically compared, especially for complex landslides. Large, slow rock slope deformations, characterized by low displacement rates (<50 mm/year) and spatial and temporal heterogeneities, are an excellent testing ground to explore the best approaches to exploit PSI data from Sentinel-1 for kinematic characterization. For three case studies, we extract profiles of different kinematic quantities using different strategies and evaluate them against field data and simplified numerical modelling. We suggest that C-band PSI data allow for an effective appraisal of complex landslide kinematics, provided that the interpretation is (a) based on decomposed velocity vector descriptors, (b) extracted along critical profiles using interpolation techniques respectful of landslide heterogeneity, and (c) constrained by suitable model-based templates and field data.

Measuring the radial flow velocity field of yield stress fluids (YSFs) between two parallel disks provides crucial data to understand the underlying flow phenomena. However, direct velocimetry of YSFs in the radial flow configuration remains a challenge, due to the complex fluid rheology and geometry constraints. In this paper, we present an experimental device for measuring YSF radial flow velocity profiles. Ultrasound Velocity Profiling (UVP) is used to non-intrusively measure the velocity profiles. The Tikhonov regularization method is implemented to obtain smooth velocity profiles, which are used to calculate the plug-flow region. Compared to our previous work on radial flow, the current contributions include: (i) additional structural frame members to maintain a constant aperture, (ii) wall slip reduction, and (iii) an improved velocity profile plug-detection algorithm. The results show that the experimental device and the measurement method are effective for further studying radial flow behavior of YSFs for industrial applications., Not duplicate with DiVA 1606821 which is an accepted manuscript.QC 20211215

This research was conducted to verify the use of additive manufacturing in producing pressure drop components inside fluid loops. A design was studied through Computation Fluid Dynamics modeling and produced using different additive manufacturing methods. A scaled loop was also designed to measure the performance and viability of the components. One component, the Packed Bed, proved to be a viable replacement using computational methods. The other component, the Helical, requires design modifications to mitigate pulsing behavior to be a viable replacement., Ensign, United States Navy, Approved for public release. Distribution is unlimited.

Reverse time migration (RTM) solves the acoustic or elastic wave equation by means of the extrapolation from source and receiver wavefield in time. A migrated image is obtained by applying a criteria known as imaging condition. The cross-correlation between source and receiver wavefields is the commonly used imaging condition. However, this imaging condition produces spatial low-frequency noise, called artifacts, due to the unwanted correlation of the diving, head and backscattered waves. Several techniques have been proposed to reduce the artifacts occurrence. Derivative operators as Laplacian are the most frequently used. In this work, we propose a technique based on a spiral phase filter ranging from 0 to 2p, and a toroidal amplitude bandpass filter, known as Laguerre-Gauss transform. Through numerical experiments we present the application of this particular filter on three synthetic data sets. In addition, we present a comparative spectral study of images obtained by the zero-lag cross-correlation imaging condition, the Laplacian filtering and the Laguerre-Gauss filtering, showing their frequency features. We also present evidences not only with simulated noisy velocity fields but also by comparison with the model velocity field gradients that this method improves the RTM images by reducing the artifacts and notably enhance the reflective events. © 2017 Sociedade Brasileira de Geofísica.

Kinematics is a key component of a landslide hazard because landslides moving at similar rates can affect structures or collapse differently depending on their mechanisms. While a complete definition of landslide kinematics requires integrating surface and subsurface site investigation data, its practical estimate is usually based on 2D profiles of surface slope displacements. These can be now measured accurately using Persistent Scatterer InSAR (PSI), which exploits open access satellite imagery. Although 2D profiles of kinematic quantities are easy to retrieve, the efficacy of possible descriptors and extraction strategies has not been systematically compared, especially for complex landslides. Large, slow rock slope deformations, characterized by low displacement rates (<50 mm/year) and spatial and temporal heterogeneities, are an excellent testing ground to explore the best approaches to exploit PSI data from Sentinel-1 for kinematic characterization. For three case studies, we extract profiles of different kinematic quantities using different strategies and evaluate them against field data and simplified numerical modelling. We suggest that C-band PSI data allow for an effective appraisal of complex landslide kinematics, provided that the interpretation is (a) based on decomposed velocity vector descriptors, (b) extracted along critical profiles using interpolation techniques respectful of landslide heterogeneity, and (c) constrained by suitable model-based templates and field data.

[EN] The study of the hydraulic jump developed in stilling basins is complex to a high degree due to the intense velocity and pressure fluctuations and the significant air entrainment. It is this complexity, bound to the practical interest in stilling basins for energy dissipation purposes, which brings the importance of physical modeling into the spotlight. However, despite the importance of stilling basins in engineering, bibliographic studies have traditionally focused on the classical hydraulic jump. Therefore, the objective of this research was to study the characteristics of the hydraulic jump in a typified USBR II stilling basin, through a physical model. The free surface profile and the velocity distribution of the hydraulic jump developed within this structure were analyzed in the model. To this end, an experimental campaign was carried out, assessing the performance of both, innovative techniques such as the time-of-flight camera and traditional instrumentation like the Pitot tube. The results showed a satisfactory representation of the free surface profile and the velocity distribution, despite some discussed limitations. Furthermore, the instrumentation employed revealed the important influence of the energy dissipation devices on the flow properties. In particular, relevant di erences were found for the hydraulic jump shape and the maximum velocity positions within the measured vertical profiles, when compared to classical hydraulic jumps.

QC 20190521

QC 20190521

QC 20190521

[EN] The study of the hydraulic jump developed in stilling basins is complex to a high degree due to the intense velocity and pressure fluctuations and the significant air entrainment. It is this complexity, bound to the practical interest in stilling basins for energy dissipation purposes, which brings the importance of physical modeling into the spotlight. However, despite the importance of stilling basins in engineering, bibliographic studies have traditionally focused on the classical hydraulic jump. Therefore, the objective of this research was to study the characteristics of the hydraulic jump in a typified USBR II stilling basin, through a physical model. The free surface profile and the velocity distribution of the hydraulic jump developed within this structure were analyzed in the model. To this end, an experimental campaign was carried out, assessing the performance of both, innovative techniques such as the time-of-flight camera and traditional instrumentation like the Pitot tube. The results showed a satisfactory representation of the free surface profile and the velocity distribution, despite some discussed limitations. Furthermore, the instrumentation employed revealed the important influence of the energy dissipation devices on the flow properties. In particular, relevant di erences were found for the hydraulic jump shape and the maximum velocity positions within the measured vertical profiles, when compared to classical hydraulic jumps.

The study of flow field over the bluff body has huge contributions in aerodynamic science. A closed looped wind tunnel was employed to determine the flow field around the cylinder. Flow characteristics and flow velocity over the cylinder was observed by taking five stations in the different regions around the rotating and non- rotating cylinder. Four stations were taken in the upstream and downstream and one was in origin. Two free stream velocities were taken for two different Reynolds numbers. Three tube yaw meter was used to calculate the total and local pressure. Flow velocity and its direction was calculated by using total pressure and static pressure with the help of Bernoulli’s principle. Yaw meter was adjusted to the inclined manometer to determine the manometric height of the total and local pressure. By using manometric height velocity was evaluated. Same process was followed while the cylinder was in rotation. A dc power supply was used to rotate the dc motor. The motor was rotated using a certain voltage for which the rpm had a fixed value. A MATLAB code for analysis of the velocity vector field was employed to visualize flow characteristics around the cylinder.

The second-order differential equation with a general polynomial solution [1], is adapted for simulation of complex velocity profile inside the turbulent boundary layer. Consequently, the simulation strategy is suggested.

The past few decades have been marked by an immense interest of the scientific community in making better use of renewable energy sources, particularly wind energy. One of the suggestions is to increase the number of small-scale vertical-axis wind turbines in urban environment. However, given that they mostly operate in adverse conditions (irregular wind speeds, Earth's boundary layer, vortex trail of surrounding objects), it is necessary to pay special attention to the numerical and experimental estimation of their performances. The conceptual design of small-scale wind turbines usually begins with detailed simulations of the encompassing flow field. Considered medium-solidity wind turbine rotor comprises three straight blades. Its aerodynamic analysis is complex since blades undergo a wide range of angles-of-attack during every rotation. This induces numerous flow instabilities, separation and interaction between the oncoming blade and the vortex trail detached from the previous. Those are some of the main reasons for the decreased efficiency of this type of wind turbines. On the other hand, their main advantages include: structural simplicity, omnidirectional operability as well as operability in "dirty" winds. Three-dimensional numerical simulations of fluid flow around a small-scale vertical-axis wind turbine have been completed for ten different working regimes. Transient computations of incompressible, viscous flow have been performed by finite volume method. Aerodynamic performances of the investigated rotor in idealized, uniform velocity stream and a power-law profile (corresponding to Earth's boundary layer) have also been compared. Computed values of power coefficient indicate that a performance reduction of 1-4 % can be expected in real working conditions.

QC 20190521

QC 20190521

Air assisted sprayers are currently used for the applications of plant protection products in fruit trees and vineyards. However, the use of these equipment carries a high environmental risk, mainly owing to the generation of airborne spray drift in the lower boundary layer above crop canopy. Hence, many tests are currently focused on investigating several factors that affect the efficiency of the spray process, in which air assistance and air behaviour are two of the most difficult parameters to evaluate. This present work proposes a first approach on the characterization of the airflow generated by an orchard sprayer equipped with an axial fan and an air reverse system in the outlet plane of the air, while circulated through two artificial rows of canopy representing vineyard trellis, using 3D-ultrasonic anemometers to measure the experimental data., Postprint (updated version)

Flow within vegetation is one of the main driving forces for material exchange and energy transfer in wetland systems. Impacted by vegetation, the flow velocity profile illustrates distortions to the classic logarithmic velocity profile and has attracted much attention among researchers. Different from analytical models of velocity distribution in literature, which is mainly suitable for vegetation with uniform frontal width, this paper establishes new analytical solutions of the velocity profile for vegetation such as shrub and sedge that have a variable frontal width in the vertical direction. A new shape function is proposed under these conditions in which the frontal width exhibits a gradual increase in the vertical direction from bottom up in the vegetation. Along with different closure models for eddy viscosity in the vegetation layer and surface layer, analytical solutions of the velocity profile are derived from the momentum equations. Good agreement between calculated and measured data shows our analytical model is effective in predicting velocity profiles., Peer Reviewed, Postprint (author's final draft)

This study experimentally investigates the effects of pore density, inlet velocity and blockage ratio on fluid flow behaviour and pressure drop in channels partially filled with a metal foam block. The fluid velocities in the free stream region, which is a clear (from foam) region on the top of foam block, are measured using Laser Doppler Anemometry (LDA) and hot-wire anemometry. The metal foam data are compared to those of solid blocks with the same size. For low blockage ratios, i.e. thin foam layers, the pressure drop caused by a solid block is higher than that of the foam when tested under identical conditions. Interestingly, nonetheless, beyond a threshold blockage ratio value, the pressure drop induced by the metal foam block exceeds that of the solid block of the same height tested at the same air flow rate. This behaviour is best described as the interplay between resistance caused by blockage versus that of the wake forms downstream and over the objects and additional frictional effects within the porous region and on the interface. Furthermore, a correlation, with ±16% deviation, is developed to predict the flow resistance caused by the solid and foam blocks across the partially filled channel.

The instruments used to quantify physical quantities require periodic calibrations to ensure the reliability and accuracy of their measurements. One of the most widely used anemometer calibration methods is the direct comparison of the readings obtained by the anemometer to be calibrated and by a standard instrument, through exposing both instruments to a gas at the same speed within a wind tunnel. The presence of the anemometer being calibrated creates an obstruction that can distort the speed profile inside the wind tunnel. Although, the objective of the present research was studying and modeling the effect of the obstructions caused by the anemometers under test on the velocity profiles inside the wind tunnel WSL 20, of the CDT de Gas, and thus to evaluate their influence on the calibration processes of instruments. The results show that type L Pitot tubes do not cause a significant distortion on the velocity profile, whereas rotating anemometers of different dimensions cause increases in the registered speed by the master that varied between 2,5% and 5,6%. Considering the effect of the obstructions inside the wind tunnel and quantifying the bias caused by them is relevant to avoid a systematic error in the calibration process., Los instrumentos utilizados para cuantificar magnitudes físicas requieren de calibraciones periódicas, para garantizar la fiabilidad y precisión de sus mediciones. Uno de los métodos de calibración de anemómetros más utilizados consiste en la comparación directa de las lecturas obtenidas por el anemómetro que se desea calibrar y por un instrumento patrón, al exponer ambos instrumentos a un gas a la misma velocidad en el interior de un túnel de viento. La presencia del anemómetro que está siendo calibrado supone una obstrucción que puede distorsionar el perfil de velocidad al interior del túnel de viento. La presente investigación tuvo como objetivo estudiar y modelar el efecto de las obstrucciones causadas por los anemómetros bajo prueba sobre los perfiles de velocidad al interior del túnel de viento WSL 20, de la Corporación CDT de Gas, y así evaluar su influencia sobre los procesos de calibración de instrumentos. Se concluye que el tamaño del anemómetro bajo prueba tiene efecto sobre la velocidad de gas registrada por el instrumento patrón. Los resultados muestran que el tubo de Pitot tipo L no causa una distorsión significativa en el perfil de velocidad, mientras que anemómetros rotativos de diferentes dimensiones ocasionan incrementos en la velocidad registrada por el patrón que varían entre 2,5 % y 5,6 %. Se evidencia la importancia de considerar el efecto de las obstrucciones al interior del túnel de viento y de cuantificar el sesgo que ocasionan, para evitar que este hecho se convierta en un error sistemático dentro del proceso de calibración.

The instruments used to quantify physical quantities require periodic calibrations to ensure the reliability and accuracy of their measurements. One of the most widely used anemometer calibration methods is the direct comparison of the readings obtained by the anemometer to be calibrated and by a standard instrument, through exposing both instruments to a gas at the same speed within a wind tunnel. The presence of the anemometer being calibrated creates an obstruction that can distort the speed profile inside the wind tunnel. Although, the objective of the present research was studying and modeling the effect of the obstructions caused by the anemometers under test on the velocity profiles inside the wind tunnel WSL 20, of the CDT de Gas, and thus to evaluate their influence on the calibration processes of instruments. The results show that type L Pitot tubes do not cause a significant distortion on the velocity profile, whereas rotating anemometers of different dimensions cause increases in the registered speed by the master that varied between 2,5% and 5,6%. Considering the effect of the obstructions inside the wind tunnel and quantifying the bias caused by them is relevant to avoid a systematic error in the calibration process., Los instrumentos utilizados para cuantificar magnitudes físicas requieren de calibraciones periódicas, para garantizar la fiabilidad y precisión de sus mediciones. Uno de los métodos de calibración de anemómetros más utilizados consiste en la comparación directa de las lecturas obtenidas por el anemómetro que se desea calibrar y por un instrumento patrón, al exponer ambos instrumentos a un gas a la misma velocidad en el interior de un túnel de viento. La presencia del anemómetro que está siendo calibrado supone una obstrucción que puede distorsionar el perfil de velocidad al interior del túnel de viento. La presente investigación tuvo como objetivo estudiar y modelar el efecto de las obstrucciones causadas por los anemómetros bajo prueba sobre los perfiles de velocidad al interior del túnel de viento WSL 20, de la Corporación CDT de Gas, y así evaluar su influencia sobre los procesos de calibración de instrumentos. Se concluye que el tamaño del anemómetro bajo prueba tiene efecto sobre la velocidad de gas registrada por el instrumento patrón. Los resultados muestran que el tubo de Pitot tipo L no causa una distorsión significativa en el perfil de velocidad, mientras que anemómetros rotativos de diferentes dimensiones ocasionan incrementos en la velocidad registrada por el patrón que varían entre 2,5 % y 5,6 %. Se evidencia la importancia de considerar el efecto de las obstrucciones al interior del túnel de viento y de cuantificar el sesgo que ocasionan, para evitar que este hecho se convierta en un error sistemático dentro del proceso de calibración.

A sub-micron resolution optical coherence tomography device was used together with a pipe rheometer to analyze the rheology and flocculation dynamics of a 0.5% microfibrillated cellulose (MFC) suspension. The bulk behavior of the MFC suspension showed typical shear thinning (power-law) behavior. This was reflected in a monotonously decreasing floc size when the shear stress exceeded the yield stress of the suspension. The quantitative viscous behavior of the MFC suspension changed abruptly at the wall shear stress of 10 Pa, which was reflected in a simultaneous abrupt drop of the floc size. The flocs were strongly elongated with low shear stresses. With the highest shear stresses, the flocs were almost spherical, indicating a good level of fluidization of the suspension.

Wind tunnel tests of wind influence on ground objects require proper experimental modeling of the atmospheric boundary layer (ABL). The authors have performed computational analyses with an aim to establish a reliable computational algorithm that could resemble complex flow patterns in wind tunnels with various obstacles, used to simulate appropriate velocity profiles within the ABL. For experimental verifications, measurements from two experimental facilities were applied, with speeds ranging from 1-4 m/s in the first, and 45 m/s in the second. For all considered cases, good agreements between the measured and computed speed profiles for operational engineering purposes have been achieved. In the sense of qualitative analyses, calculated contours of velocity magnitude and eddy viscosity inside the wind tunnel test sections have verified that good homogeneity of the simulated ABL in both wind tunnels had been established in the domains where velocity profiles were measured. Presented results have shown the capability of here established calculation model to resemble a number of costly wind tunnel test hours during preparations of proper obstacle arrangements for experimental ABL modeling in a wide wind speed range, and thus reduce the overall project costs. Also, presented CFD algorithm can readily be calibrated and used for engineering research of wind effects on different ground objects, as a virtual wind tunnel.

River discharge has to be monitored reliably for effective water management. As river discharge cannot be measured directly, it is usually inferred from the water level. This practice is unreliable at places where the relation between water level and flow velocity is ambiguous. In such a case, the continuous measurement of the flow velocity can improve the discharge prediction. The emergence of horizontal acoustic Doppler current profilers (HADCPs) has made it possible to continuously measure the flow velocity. However, the profiling range of HADCPs is limited, so that a single instrument can only partially cover a wide cross section. The total discharge still has to be determined with a model. While the limitations of rating curves are well understood, there is not yet a comprehensive theory to assess the accuracy of discharge predicted from velocity measurements. Such a theory is necessary to discriminate which factors influence the measurements, and to improve instrument deployment as well as discharge prediction. This paper presents a generic method to assess the uncertainty of discharge predicted from range-limited velocity profiles. The theory shows that a major source of error is the variation of the ratio between the local and cross-section-averaged velocity. This variation is large near the banks, where HADCPs are usually deployed and can limit the advantage gained from the velocity measurement. We apply our theory at two gauging stations situated in the Kapuas River, Indonesia. We find that at one of the two stations the index velocity does not outperform a simple rating curve.

A rheometric method based on velocity profiling by optical coherence tomography (OCT) was used in the analysis of rheological and boundary layer flow properties of a 0.5% microfibrillated cellulose (MFC) suspension. The suspension showed typical shear thinning behaviour of MFC in the interior part of the tube, but the measured shear viscosities followed interestingly two successive power laws with an identical flow index (exponent) and a different consistency index. This kind of viscous behaviour, which has not been reported earlier for MFC, is likely related to a sudden structural change of the suspension. The near-wall flow showed existence of a slip layer of 2–12 μm thickness depending on the flow rate. Both the velocity profile measurement and the amplitude data obtained with OCT indicated that the slip layer was related to a concentration gradient appearing near the tube wall. Close to the wall the fluid appeared nearly Newtonian with high shear rates, and the viscosity approached almost that of pure water with decreasing distance from the wall. The flow rates given by a simple model that included the measured yield stress, viscous behavior, and slip behavior, was found to give the measured flow rates with a good accuracy.

Differences in the rheology and friction factor of natural food hydrocolloid gels were studied in this paper. The practical importance of the knowledge of the rheological parameters is quite evident. The experimental data were carried out using a concentric cylinder rotary viscometer. It was prepared 1% hydrocolloid solutions (hydrogels). Hydrogels of the natural gums extracted from the seeds of the plants and plant tubers have been used - carob gum (from the seeds of Ceratonia siliqua), guar gum (from the seeds of Cyamopsis tetragonoloba) and tara gum (from the seeds of Caesalpinia spinosa). Rheological behaviour has non-Newtonian pseudoplastic character and the flow curves were fitted using the Otswald - de Waele (power law) model and Herschel - Bulkley model. The hydrogels exhibit shear thinning behaviour. The meaning of the rheological parameters on the friction factors during flow of hydrocolloid gels in the tube has been shown. Information on time dependent behaviour of tested liquids has been also obtained. Time dependent curves were fitted by the Gaussian model. Preliminary results obtained for a constant shear rate showed the thixotropic and time-dependent behaviour of the hydrogels. These parameters can be especially used in much software dealing with a numerical simulation of the flow problems., info:eu-repo/semantics/openAccess

Differences in the rheology and friction factor of natural food hydrocolloid gels were studied in this paper. The practical importance of the knowledge of the rheological parameters is quite evident. The experimental data were carried out using a concentric cylinder rotary viscometer. It was prepared 1% hydrocolloid solutions (hydrogels). Hydrogels of the natural gums extracted from the seeds of the plants and plant tubers have been used - carob gum (from the seeds of Ceratonia siliqua), guar gum (from the seeds of Cyamopsis tetragonoloba) and tara gum (from the seeds of Caesalpinia spinosa). Rheological behaviour has non-Newtonian pseudoplastic character and the flow curves were fitted using the Otswald - de Waele (power law) model and Herschel - Bulkley model. The hydrogels exhibit shear thinning behaviour. The meaning of the rheological parameters on the friction factors during flow of hydrocolloid gels in the tube has been shown. Information on time dependent behaviour of tested liquids has been also obtained. Time dependent curves were fitted by the Gaussian model. Preliminary results obtained for a constant shear rate showed the thixotropic and time-dependent behaviour of the hydrogels. These parameters can be especially used in much software dealing with a numerical simulation of the flow problems.

Differences in the rheology and friction factor of natural food hydrocolloid gels were studied in this paper. The practical importance of the knowledge of the rheological parameters is quite evident. The experimental data were carried out using a concentric cylinder rotary viscometer. It was prepared 1% hydrocolloid solutions (hydrogels). Hydrogels of the natural gums extracted from the seeds of the plants and plant tubers have been used - carob gum (from the seeds of Ceratonia siliqua), guar gum (from the seeds of Cyamopsis tetragonoloba) and tara gum (from the seeds of Caesalpinia spinosa). Rheological behaviour has non-Newtonian pseudoplastic character and the flow curves were fitted using the Otswald - de Waele (power law) model and Herschel - Bulkley model. The hydrogels exhibit shear thinning behaviour. The meaning of the rheological parameters on the friction factors during flow of hydrocolloid gels in the tube has been shown. Information on time dependent behaviour of tested liquids has been also obtained. Time dependent curves were fitted by the Gaussian model. Preliminary results obtained for a constant shear rate showed the thixotropic and time-dependent behaviour of the hydrogels. These parameters can be especially used in much software dealing with a numerical simulation of the flow problems., info:eu-repo/semantics/openAccess

Differences in the rheology and friction factor of natural food hydrocolloid gels were studied in this paper. The practical importance of the knowledge of the rheological parameters is quite evident. The experimental data were carried out using a concentric cylinder rotary viscometer. It was prepared 1% hydrocolloid solutions (hydrogels). Hydrogels of the natural gums extracted from the seeds of the plants and plant tubers have been used - carob gum (from the seeds of Ceratonia siliqua), guar gum (from the seeds of Cyamopsis tetragonoloba) and tara gum (from the seeds of Caesalpinia spinosa). Rheological behaviour has non-Newtonian pseudoplastic character and the flow curves were fitted using the Otswald - de Waele (power law) model and Herschel - Bulkley model. The hydrogels exhibit shear thinning behaviour. The meaning of the rheological parameters on the friction factors during flow of hydrocolloid gels in the tube has been shown. Information on time dependent behaviour of tested liquids has been also obtained. Time dependent curves were fitted by the Gaussian model. Preliminary results obtained for a constant shear rate showed the thixotropic and time-dependent behaviour of the hydrogels. These parameters can be especially used in much software dealing with a numerical simulation of the flow problems., info:eu-repo/semantics/openAccess

People who suffer from swallowing disorders, commonly referred to as dysphagia, are often restricted to a texture-modified diet. In such a diet, the texture of the fluid is modified mainly by the addition of gum or starch-based thickeners. For optimal modification of the texture, tunable rheological parameters are shear viscosity, yield stress, and elasticity. In this work, the flow properties of commercial thickeners obtained from major commercial suppliers were measured both in shear and extensional flow using a laboratory viscometer and a newly developed tube viscometry technique, termed Pulsed Ultrasound Velocimetry plus Pressure Drop (PUV+PD). The two methods gave similar results, demonstrating that the PUV+PD technique can be applied to study flow during the swallowing process in geometry similar to that of the swallowing tract. The thickeners were characterized in relation to extensional viscosity using the Hyperbolic Contraction Flow method, with microscopy used as a complementary method for visualization of the fluid structure. The gum-based thickeners had significantly higher extensional viscosities than the starch-based thickeners. The rheological behavior was manifested in the microstructure as a hydrocolloid network with dimensions in the nanometer range for the gum-based thickeners. The starch-based thickeners displayed a granular structure in the micrometer range. In addition, the commercial thickeners were compared to model fluids (Boger, Newtonian, and Shear-thinning) set to equal shear viscosity at 50/s and it was demonstrated that their rheological behavior could be tuned between highly elastic, extension-thickening to Newtonian. Practical applications: Thickeners available for dysphagia management were characterized for extensional viscosity to improve the understanding of these thickeners in large scale deformation. Extensional deformation behavior was further explained by using microcopy as corresponding technique for better understanding of st

When the capacity of the spillway of a dam is exceeded for a given flood, overtopping occurs; in such cases potentially dangerous hydrodynamic actions and scour downstream of the dam need to be foreseen. Detailed studies of jets impinging in plunge pools from overflow nappe flows are scarce. This work addresses plunge pool flows, and compares numerical results against our own experiments. The energy dissipation is larger than 75% of the impingement jet energy. Instantaneous velocities and air entrainment were obtained with the use of an Acoustic Doppler Velocimeter and optical fibre probe, respectively. Mean velocity field and turbulence kinetic energy profiles were determined. To identify the level of reliability of models, numerical simulations were carried out by using the ‘homogeneous’ model of ANSYS CFX, together with different turbulence closures. The numerical results fall fairly close to the values measured in the laboratory, and with expressions for submerged hydraulic jumps and horizontal wall jets. The observations can be well predicted for characterized profiles at a minimum distance of 0.40 m downstream from the stagnation point, horizontal velocities greater than 40% of the maximum velocity in each profile, and when the ratio of the water cushion depth to the jet thickness is lower than 20.

Obstacles like forests, ridges and hills can strongly affect the velocity profile in front of a wind turbine rotor. The present work aims at quantifying the influence of nearby located obstacles on the performance and wake characteristics of a downstream located wind turbine. Here the influence of an obstacle in the form of a cylindrical disk was investigated experimentally in a water flume. A model of a three-bladed rotor, designed using Glauert's optimum theory at a tip speed ratio λ = 5, was placed in the wake of a disk with a diameter close to the one of the rotor. The distance from the disk to the rotor was changed from 4 to 8 rotor diameters, with the vertical distance from the rotor axis varied 0.5 and 1 rotor diameters. The associated turbulent intensity of the incoming flow to the rotor changed 3 to '6% due to the influence of the disk wake. In the experiment, thrust characteristics and associated pulsations as a function of the incoming flow structures were measured by strain gauges. The flow condition in front of the rotor was measured with high temporal accuracy using LDA and power coefficients were determine as function of tip speed ratio for different obstacle positions. Furthermore, PIV measurements were carried out to study the development of the mean velocity deficit profiles of the wake behind the wind turbine model under the influence of the wake generated by the obstacle. By use of regression techniques to fit the velocity profiles it was possible to determine velocity deficits and estimate length scales of the wake attenuation.

The fluid mechanics of microfluidics is distinctively simpler than the fluid mechanics of macroscopic systems. In macroscopic systems effects such as non-laminar flow, convection, gravity etc. need to be accounted for all of which can usually be neglected in microfluidic systems. Still, there exists only a very limited selection of channel cross-sections for which the Navier-Stokes equation for pressure-driven Poiseuille flow can be solved analytically. From these equations, velocity profiles as well as flow rates can be calculated. However, whenever a cross-section is not highly symmetric (rectangular, elliptical or circular) the Navier-Stokes equation can usually not be solved analytically. In all of these cases, numerical methods are required. However, in many instances it is not necessary to turn to complex numerical solver packages for deriving, e.g., the velocity profile of a more complex microfluidic channel cross-section. In this paper, a simple spreadsheet analysis tool (here: Microsoft Excel) will be used to implement a simple numerical scheme which allows solving the Navier-Stokes equation for arbitrary channel cross-sections.

Since eddies play a major role in the dynamics of oceanic flows, it is of great interest to detect them and gain information about their tracks, their lifetimes and their shapes. We present a Lagrangian descriptor based on the modulus of vorticity to construct an eddy tracking tool. In our approach we denote an eddy as a rotating region in the flow possessing an eddy core corresponding to a local maximum of the Lagrangian descriptor and enclosed by pieces of manifolds of distinguished hyperbolic trajectories (eddy boundary). We test the performance of the eddy tracking tool based on this Lagrangian descriptor using an convection flow of four eddies, a synthetic vortex street and a velocity field of the western Baltic Sea. The results for eddy lifetime and eddy shape are compared to the results obtained with the Okubo–Weiss parameter, the modulus of vorticity and an eddy tracking tool used in oceanography. We show that the vorticity-based Lagrangian descriptor estimates lifetimes closer to the analytical results than any other method. Furthermore we demonstrate that eddy tracking based on this descriptor is robust with respect to certain types of noise, which makes it a suitable method for eddy detection in velocity fields obtained from observation.

The fluid mechanics of microfluidics is distinctively simpler than the fluid mechanics of macroscopic systems. In macroscopic systems effects such as non-laminar flow, convection, gravity etc. need to be accounted for all of which can usually be neglected in microfluidic systems. Still, there exists only a very limited selection of channel cross-sections for which the Navier-Stokes equation for pressure-driven Poiseuille flow can be solved analytically. From these equations, velocity profiles as well as flow rates can be calculated. However, whenever a cross-section is not highly symmetric (rectangular, elliptical or circular) the Navier-Stokes equation can usually not be solved analytically. In all of these cases, numerical methods are required. However, in many instances it is not necessary to turn to complex numerical solver packages for deriving, e.g., the velocity profile of a more complex microfluidic channel cross-section. In this paper, a simple spreadsheet analysis tool (here: Microsoft Excel) will be used to implement a simple numerical scheme which allows solving the Navier-Stokes equation for arbitrary channel cross-sections.

A numerical code is developed for the transition-prediction of boundary layer using the e(exp N) method. The main advantage that the present code offers over the SALLY code developed by NASA is in combination with Navier-Stokes solver for the calculation of the velocity profile of the boundary layer. By comparison with the results from the present code to the SALLY code, it was found that accuracy of the former code is better than the latter one., e(exp N)法を用いた境界層の遷移予測の数値コードを開発した。本コードが、NASAにより開発されたSALLYコードより優れた点は、境界層における速度分布の計算にナビエ・ストークス方程式を用いた解法を併用しているところにある。本コードとSALLYコードの結果を比較すると前者の精度が後者よりも優れていることが分かった。

Background: An ablation catheter with integrated high-frequency single element ultrasound transducers has been developed by Philips Research, which makes it possible to assess tissue-depth and lesion formation in real-time. The interpretation of the acquired ultrasound M-mode images is difficult due to a combination of cardiac motion and motion of the catheter itself. Objective The aim of this study is to develop and validate a simulation model that includes catheter and tissue motion and use this as a tool to gain insights in the effects of catheter motion on M-mode images and corresponding velocity profiles. Method A 2D simulation model, of a moving catheter with three integrated ultrasound transducers that observe contracting tissue, was developed. Comparison of simulated data with real ultrasound data was performed, among other tests, to validate the 2D simulation model. Validation criteria were based on predefined requirements. The validated simulation model was used to generate seventeen different output datasets varying with the frequency and amplitude of the cardiac \& catheter motion input signals. These datasets were used to analyse the effect of catheter motion on M-mode images and corresponding velocity profiles. Results The validation tests imply that the simulated data can serve as reliable replacements for real ultrasound data. Findings from the analysis of the simulated data suggest that cardiac velocity is underestimated when the catheter angle deviates from its perpendicular state in relation to the tissue and is overestimated when the catheter angle moves back to its perpendicular state. Moreover, when catheter motion dominates over cardiac motion the cardiac velocity may be estimated in the opposite direction as the actual direction of cardiac motion. Conclusion The validation tests insinuate that the simulation model meets the predefined requirements. The simulation increases understanding of the relation between catheter \& cardiac motion in M, BME, BioMechanical Engineering, Mechanical, Maritime and Materials Engineering

Background: An ablation catheter with integrated high-frequency single element ultrasound transducers has been developed by Philips Research, which makes it possible to assess tissue-depth and lesion formation in real-time. The interpretation of the acquired ultrasound M-mode images is difficult due to a combination of cardiac motion and motion of the catheter itself. Objective The aim of this study is to develop and validate a simulation model that includes catheter and tissue motion and use this as a tool to gain insights in the effects of catheter motion on M-mode images and corresponding velocity profiles. Method A 2D simulation model, of a moving catheter with three integrated ultrasound transducers that observe contracting tissue, was developed. Comparison of simulated data with real ultrasound data was performed, among other tests, to validate the 2D simulation model. Validation criteria were based on predefined requirements. The validated simulation model was used to generate seventeen different output datasets varying with the frequency and amplitude of the cardiac \& catheter motion input signals. These datasets were used to analyse the effect of catheter motion on M-mode images and corresponding velocity profiles. Results The validation tests imply that the simulated data can serve as reliable replacements for real ultrasound data. Findings from the analysis of the simulated data suggest that cardiac velocity is underestimated when the catheter angle deviates from its perpendicular state in relation to the tissue and is overestimated when the catheter angle moves back to its perpendicular state. Moreover, when catheter motion dominates over cardiac motion the cardiac velocity may be estimated in the opposite direction as the actual direction of cardiac motion. Conclusion The validation tests insinuate that the simulation model meets the predefined requirements. The simulation increases understanding of the relation between catheter \& cardiac motion in M, BME, BioMechanical Engineering, Mechanical, Maritime and Materials Engineering