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This paper proposes an improved design methodology and global optimization method for the design of an advanced dropped-hinge flap (ADHF) using an integrated approach. The approach implemented an a...

The three-dimensional steady incompressible numerical results of an isothermal flowfield resulting from the interaction of two swirl-stabilized air nozzles in a multiple lean direct injection combu...

An accurate prediction of the hydrogen behaviors in the accident and management process is a crucial topic for both the hydrogen safety assessment and safety analysis in the confined enclosure like the containment of the nuclear power plant (NPP). Hence, the hydrogen behaviors including the transient light gas release, stratification and dissolution in the TH22 test facility for the NPP containment are analyzed and compared using the 3-D CFD code GASFLOW-MPI in this study. In this paper, the light gas helium is adopted as a substitute for the hydrogen in the calculations in accordance with the experiment. Firstly, the detached eddy simulation (DES) turbulence model, 3-D numerical model and experiment setup are introduced. Then, the hydrogen behaviors with the GASFLOW-MPI including the light gas release, stratification and dissolution are analyzed and validated with the experiment data. In addition, the velocity profiles, light gas concentrations, dimensionless numbers and temperature distributions are evaluated for the characteristics of the hydrogen behaviors. The results indicate that the calculation results agree well with the experiment data. Foremostly, the relative errors between the calculation results and experiment data during the phase of the dissolution of the light gas cloud are within 11.9%. Meanwhile, the relative errors of the time for the complete dissolution during the phase of the dissolution of the light gas cloud are within 5.0%. For the light gas release and stratification phase, the jet flow dominates as the Froude (Fr) number exceeds 10 during the time t = 600 s–800 s. Additionally, the time averaged centerline velocity and light gas concentration after the potential core region decay with a slop of 1/z which coincide with the theoretical jet limit. Lastly, the light gas concentrations and temperature distributions in all three phases are captured clearly with the GAFLOW-MPI. It demonstrates that the GASFLOW-MPI can accurately described the details of the related hydrogen behaviors in the accident and management process in the confined enclosure like the NPP. This paper can provide guidance for the numerical computation of the hydrogen safety issues in the confined space.

This study investigates the atomization process of a liquid jet in supersonic crossflow at a Mach number of 2.1 by using a multi-scale simulation method. This hybrid numerical method can realize accurate simulation of the primary and secondary breakup of the liquid jet with large scale instabilities and small droplet dynamics under compressible supersonic crossflow. The Eulerian framework is applied for capturing the gas-liquid interface by a coupled Level set and Volume-of-fluid (CLSVOF) method. Based on the Delayed Detached Eddy Simulation (DDES), the adaptive mesh refinement (AMR) method is introduced to predict the breakup of liquid column, blocks and filaments. The Lagrangian framework is applied for the dispersed droplets generated under the conversion criteria during the atomization process. The hybrid CLSVOF-LPT method can greatly reduce the loss of liquid phase mass and save computing resources. The distribution morphology of droplets in a cross-sectional plane from the simulation agreed well with the experimental data. Besides, the trends of the jet trajectory and primary breakup behavior of liquid column are well captured.

A low-order method is presented for aerodynamic prediction of wings operating at near-stall and post-stall flight conditions. The method is intended for use in design, modeling, and simulation. In this method, the flow separation due to stall is modeled in a vortex-lattice framework as an effective reduction in the camber, or "decambering." For each section of the wing, a parabolic decambering flap, hinged at the separation location of the section, is calculated through iteration to ensure that the lift and moment coefficients of the section match with the values from the two-dimensional viscous input curves for the effective angle of attack of the section. As an improvement from earlier low-order methods, this method also predicts the separation pattern on the wing. Results from the method, presented for unswept wings having various airfoils, aspect ratios, taper ratios, and small, quasi-steady roll rates, are shown to agree well with experimental results in the literature, and computational solutions obtained as part of the current work., 29 pages, 28 figures. Submitted to Journal of Aircraft

The paper presents an aerodynamic investigation of 70 different streamlined bodies with fineness ratios ranging from 2 to 10. The bodies are chosen to idealize both unmanned and small manned aircra...

An efficient implicit Fourier time-spectral method is developed for the unsteady Reynolds-averaged Navier–Stokes (URANS) computations of turbulent flows. In addition to the time-spectral URANS equa...

A self-adaptive dissipation method based on a fifth-order dissipative compact scheme is proposed to reduce the numerical dissipation in separated flow. The method involves a self-adaptive operating...

A first principles physics-based simulation framework that accounts for wind-over-deck (WOD) and ground effects during approach and landing of a helicopter on a ship deck is developed. The WOD velo...

A numerical investigation of the rapid turbulent filtration combustion within a packed pebble bed is conducted at a fixed superficial velocity of 0.5 m/s, equivalence ratio of 1.0 (methane/air) und...

The diffusion process and spatial distribution of a liquid jet in supersonic crossflow (Mach number of 2) in a model combustor with an expanded section were investigated on the basis of experiments and simulations. Experiments were performed using high-speed photography, high-speed shadowgraph and laser-based particle size analyzer to investigate the spray structures, flow fields and droplet diameter, respectively. The Eulerian-Lagrangian method coupled with the Kelvin-Helmholtz/Rayleigh-Taylor breakup model were used in the simulations. Moreover, delayed detached eddy simulation numerical method based on the two-equation shear stress transport turbulence model was applied. The spray distributions and flow fields predicted in the simulation, including the spray penetration, cross-sectional distribution, droplet size in the far-field, the bow shock, large-scale vortices and recirculation zones were in good agreement with experiments. The evolution of spray in supersonic crossflow could be divided into three stages, aerodynamic induced liquid column fracturing, expansion wave promoted spray accelerating, and compression wave disturbed spray blending. Overall, the channel configuration (with expended section) changed the direction and strength of the supersonic airflow. The force of the crossflow determined the spray diffusion.

Total-pressure losses and distortion in an aggressive offset diffuser, induced by secondary-flow vortices and boundary-layer separation, are mitigated using fluidic actuation for the aerodynamic in...

This paper presents an efficient adjoint-based shape optimization framework for airframe noise reduction in which algorithmic differentiation (AD) is applied to the open-source multiphysics solver ...

Large-eddy simulations of supersonic, turbulent flow in asymmetric and symmetric planar nozzles are carried out using high-order finite difference schemes and a large-eddy simulation approach based...

The design phase of a rocket combustion chamber relies on the prediction of the wall heat fluxes, in order to optimize the components to prevent thermal damage. Based on the experimental data of a ...

In order to dynamically describe the transition of the scalar dissipation rate of the mixture fraction variance from near-wall regions to mainstream in near-wall combustion, the traditional flamelet/progress variable (FPV) model, which can be used either within the Reynolds Averaged Navier Stokes (RANS) framework or the large-eddy simulation (LES) framework, is modified to form an improved FPV model within the framework of the improved delayed detached eddy simulation (IDDES). The model blends respective expressions of the scalar dissipation rate within the RANS and LES frameworks into a unified form with an employment of the IDDES concept. It also adopts an analogy between the mixture fraction variance and turbulent kinetic energy. A hydrogen-fueled near-wall combustion is simulated to validate this model. Large-scale turbulent structures, which can either locally enhance combustion or cause local extinction in the reacting zone, are reproduced. Due to the blockage to lateral extents of spanwise turbulent structures, a three-dimensional effect, that the low temperature fluid at lower corners of flow passage is forced to move away from sidewalls, is also reproduced. The results show that the improved FPV model can avoid the scalar over-mixing effect of the traditional FPV model by delaying and mitigating the development of the mixture fraction variance at the near-wall regions. Therefore, the starting point of the high temperature zone predicted by the improved FPV model is downstream of that predicted by the traditional FPV model. It is indicated that the improved FPV model tends to delay combustion. This tendency is also demonstrated by the less combustion efficiency in the upstream region predicted by the improved FPV model. As a result, it can generate a moderate growth of the mixing and reacting zone in the longitudinal direction, which therefore improves the predictions of the species concentrations. In contrast, the traditional FPV model thickens the mixing and reacting zone, which is negative to the combustion efficiency in the downstream region. It is implied that a reasonable development of the mixture fraction variance at near-wall regions is essentially required for near-wall combustion simulation using the FPV model within the IDDES framework.

This paper conducts improved delayed detached eddy simulation (IDDES) to numerically investigate the performance of a three-dimensional (3D) aircraft control surface using coflow jet (CFJ) active f...

This work presents a numerical study of a skimming flow regime in a stepped spillway structure, which is a complex two-phase flow with self-aeration phenomenon. The numerical models employed consis...

Circulation-controlled wings using the Coanda effect over the high-lift device (i.e., the flap) potentially enhance the wing’s lift coefficient by delaying or avoiding separation of the strongly de...

The liquid jet from an airblast atomizer into supersonic air crossflow with a Mach number of 1.94 was investigated numerically. The detached eddy simulation was used as the turbulence model to compromise the merits of both large eddy simulation and k − e models. The Kelvin-Helmholtz and Rayleigh-Taylor (KHRT) model was used to simulate the droplet breakup process. The location and velocity of the child droplets are tracked efficiently by the automated tracking scheme. The model was validated using previous experimental data and a good agreement was obtained. In the present study, the airblast atomizer, which allows core and annular air flows with the injected liquid, is utilized instead of the ordinary orifice nozzle to improve the breakup process and the droplet distribution. The airblast atomizer dimensions were represented as factors of the ordinary orifice nozzle and the air mass flow rates through the atomizer were adjusted as ratios from the liquid mass flow rate. The effects of these parameters on the spray structure characteristics were presented. Then, a new proposed design for the airblast atomizer was suggested based on the improvements in spray characteristics dimensions and sauter mean diameter distribution. The core and annular air flows significantly enhanced the spray characteristic dimensions and spray breakup compared with the ordinary orifice nozzle.

Flow and noise solutions of the two Large-Eddy Simulation (LES) approaches are evaluated for the jet flow conditions corresponding to a benchmark coaxial jet case from the European Union Computatio...

The mean flowfield in the aft region of cargo aircraft configurations is analyzed using large-eddy simulations. A simplified surrogate fuselage is considered, consisting of a cylinder with axis par...

A coupled immersed boundary method and unsteady actuator surface model (IBM–ASM) is developed and implemented into a finite-volume-based incompressible Navier–Stokes solver within OpenFOAM for effi...

An advanced potential flow method is used to study the aerodynamic interactions between small rotors of quadrotor configurations and the impact on the overall flight performance. The aerodynamic an...

Flow-induced acoustic resonance in the closed side branch of a natural gas pipeline can cause intensive vibration which threatens the safe operation of the pipeline. Accurately modeling this excitation process is necessary for a workable understanding of the genetic mechanism to resolve this problem. A realizable k-ε Delayed Detached Eddy Simulation (DDES) model was conducted in this study to numerically simulate the acoustic resonance problem. The model is shown to accurately capture the acoustic resonance phenomenon and self-excited vibration characteristics with low calculation cost. The pressure pulsation component of the acoustic resonance frequency is gradually amplified and transformed into a narrowband dominant frequency in the process of acoustic resonance excitation, forming a so-called “frequency lock-in phenomenon.” The gas is pressed into and out of the branch in sinusoidal mode during excitation. The first-order frequency, single vortex moves at the branch inlet following the same pattern. A quarter wavelength steady standing wave forms in the branch. The mechanism and characteristics presented in this paper may provide guidelines for developing new excitation suppression methods.

Cavitation has a significant influence on the accurate control of the liquid filling rate and braking performance of a hydraulic retarder; however, previous studies of the flow field in hydraulic retarders have provided insufficient information in terms of considering cavitation. Here, the volume of fluid (VOF) method and a scale-resolving simulation (SRS) were employed to numerically and more comprehensively calculate and analyze the flow field in a retarder considering the cavitation phenomenon. The numerical models included the improved delayed detached eddy simulation (IDDES) model, stress-blended eddy simulation (SBES) model, dynamic large eddy simulation (DLES) model, and shear stress transport (SST) model in the Reynolds-averaged Navier-Stokes (RANS) model. All the calculations were typically validated by the brake torque in the impeller rather than the internal flow. The unsteady flow field indicated that the SBES and DLES models could better capture unsteady flow phenomena, such as the chord vortex. The SBES and DLES models could also better capture bubbles than the SST and IDDES models. Since the braking torque error of the SBES model was the smallest, the transient variation of the bubble volume fraction over time on a typical flow surface was analyzed in detail with the SBES model. It was found that bubbles mainly appeared in the center area of the blade suction surface, which coincided with the experiments. The accumulation of bubbles resulted in a larger bubble volume fraction in the center of the blade over time. In addition, the temperature variations of the pressure blade caused by heat transfer were further analyzed. More bubbles precipitated in the center of the blade, leading to a lower temperature in this area.

The combustion of low calorific value syngas in a 3.3-kW reverse-flow chamber under moderate or intense low-oxygen dilution (MILD) (global equivalence ratio Φglobal = 0.89) and ultra-lean (Φglobal = 0.32) conditions have been numerically investigated with detailed chemistry. Reynolds averaged Navier Stokes (RANS)/Detached eddy simulation (DES) models for flow and Eddy dissipation concept (EDC)/Flamelet generated manifold (FGM) models for combustion have been used. Quantitative measurements of temperature, OH radical, and CO emissions performed in the same combustor are used to validate and compare the models. The prediction of the minor species OH is a special focus of the present study. The fields of velocity, mixture fraction, and kinetic parameters have been investigated in detail. The DES-EDC model performs the best in predicting the scalar distributions, although the computational cost is highest. The RANS model predicts insufficient mixing and higher velocities leading to a delayed reaction zone. The FGM model consistently predicts early ignition that has been attributed to the lack of a suitable progress variable and the use of the diffusion flamelet to represent the thermochemistry. However, the FGM model is promising with suitable modifications due to the low computational cost. The present study also provides a comprehensive dataset in a reverse-flow chamber operating under MILD and ultra-lean conditions for validation of numerical models.

A numerical study of propagation of cohesive fluid mud gravity currents in the form of lock-exchange was done using the OpenFOAM open source toolbox. An Eulerian approach solution for three separate phases was developed by incorporating a rheological model to predict the front position of cohesive fluid mud gravity currents. The model also simulates features in the complete movement phases including slumping, self-similar, and viscous in which the dynamics of propagation are affected by the balance of viscous and buoyancy forces, and the inertia force is negligible. The influence of using different turbulence models containing sub-grid scale (SGS), modified SGS, detached eddy simulation (DES), delayed-detached eddy simulation (DDES), Launder-R eece-Rodi (LRR), and k-ɛ models on the accuracy of simulation results was evaluated by comparing with available experimental data. The results show that the selection of the proper turbulence model is one of the most important issues for this type of the numerical modeling. The more efficient turbulence model was suggested and tabulated for each stage of propagation and different selected concentrations of 1,045, 1,140, and 1,214 g/L. Although different turbulence models (except k-ɛ) lead to front propagation dynamic simulation results that are in good agreement with the experimental measurements in the early stage of propagation for low concentrations, only DES, SGS, and modified SGS are able to capture the Kelvin-Helmholtz instability vortex shapes at the dense fluid interface, which is the main characteristic of the gravity current through the slumping phase. The calculated accuracies of SGS and modified SGS in predicting gravity current propagation for the both self-similar and viscous phases also are slightly better than DES, DDES, and LRR model results. The results of this study confirmed the performance and efficiency of the modified SGS model in which the interaction coefficients between phases are calibrated for the numerical modeling of fluid mud gravity current propagation.

A numerical study using improved delayed detached eddy simulation (IDDES) was used to investigate the influence of the embankment height on the aerodynamic performance of a high-speed train travelling under the influence of a crosswind. The results of the flow predictions were used to explore both the instantaneous and the time-averaged flows and the resulting aerodynamic forces, moments and slipstreams. An increase of the aerodynamic drag and side forces as well as the lift force of the head and middle cars were observed with rising embankment height. While the lift force of the tail car decreased with the increasing embankment height. Furthermore, the height of the embankment was found to have a strong influence on the slipstream on the leeward side of the train. The correlation between the embankment height and the slipstream velocity on the windward side, was rather small. The flow structures in the near-wake of the leeward side of the train, responsible for the aerodynamic properties of the train were analyzed, showing strong dependency on the embankment height.

Small-scale vertical axis wind turbines are good candidates for urban area use where, due to various obstacles, the airflow is turbulent. In urban areas, air velocity is mostly low and site specific, so just in a few places, like tall buildings, there are suitable airflow situation in order to use turbine, so it is a good idea to install more than one turbine in such locations. On the other hand, acoustic noise that is emitted from turbines may bother people living in that area. In the current study, power performance of small-scale vertical axis wind turbines in a V-form array configuration is investigated using detached eddy simulation method. Also, Ffowcs Williams and Hawkings acoustic analogy formulation is conducted in order to predict the noise radiation level of turbines. Results showed that power performance of most of the turbines increased due to venturi effect that is made by low speed regions behind turbines. Acoustic noise analysis showed that there is a strong enhancement in sound pressure level in receivers compared with the isolated turbine.

An improved delayed detached eddy simulation based on a shear–stress transport κ–ω turbulence model is used to investigate the aerodynamic characteristics of a high-speed train with an aerodynamic braking plate installed in the inter-car gap (ICG) region. The flow field and the aerodynamic performance of high-speed trains with different aerodynamic braking plate configurations are compared and analysed. The numerical method used in this study is verified through a wind tunnel test. Results show that opening the plates installed in the ICG significantly increased the aerodynamic drag of the train, especially large downstream plates with relatively small fluctuations in the aerodynamic forces relative to those of large upstream plates. The braking plates significantly affected the levels of downstream ICG turbulence, which then interacted with the external flow to reduce the wake profile.

This Paper examines the performance of a rotor-blown-wing in hover and forward flight conditions. Flow solutions were generated using Helios, with a delayed detached eddy simulation model. The conf...

The flow field structure of a single injection port fluidic thrust vectoring nozzle was studied by introducing secondary flow injection in the expansion section of the two-dimensional convergent-divergent nozzle. To determine the motion characteristics of unsteady flow in a shock-induced fluidic vectoring nozzle, detached eddy simulation was conducted to simulate the three-dimensional flow field, and the flow mechanism in the nozzle was analyzed. Fourier mode decomposition was used to analyze the pressure coefficient on the symmetrical surface of the nozzle. Results show three natural frequencies in the flow field of the shock-induced fluidic vectoring nozzle. The first-order mode corresponding to frequency f1 = 512.8 Hz mainly illustrates the oscillation of shock waves. The second-order mode corresponding to frequency f2 = 2825 Hz illustrates the shedding of vortices. The third-order mode corresponding to frequency f3 = 4650 Hz is similar to the second-order mode; however, the spatial scales of vortices decrease.

An Improved Delayed Detached Eddy Simulation (IDDES) model as a kind of hybrid RANS/LES approach has been developed and applied to calculate tip leakage flow in a linear compressor cascade with moving casing, and the result was compared with the experimental results and LES results. The hybrid approach combines delayed detached eddy simulation (DDES) with an improved RANS–LES hybrid model aimed at wall modeling in LES (WMLES). In this code, the convective flux was solved using fourth-order skew-symmetric scheme and the Spalart–Allmaras (S–A) model was applied as a subgrid scale (SGS) model. This hybrid RANS/LES model code was successfully validated by simulation of homogeneous isotropic turbulence, turbulent channel flow, and backward facing step flow. After validation, a 3D compressor cascade tip leakage flow with different specific blade tip clearances was simulated via this code. Result shows that the blade surface pressure distribution agrees well with the results of experiment and LES. The hybrid RANS/LES model captures intensive vortices clearly, including tip leakage vortex, tip separation vortices, induced vortices, and abundant vortex structures generated by the interaction between tip separation vortices and tip leakage vortex. The end-wall vortical structures were observed in detail being described by Q vortex identification method and meanstream lines. The effect of tip-gap size on total pressure loss was investigated and it was found that there is a best tip gap with most stable tip leakage vortex and least pressure loss.

Previous research studies indicate that the proportion of Magnus force at the spinning projectile tail position is very high. Meanwhile, the large mutations of aerodynamic characteristics are found after adding boattail structures. In order to study the influences of boattail structures on aerodynamics of a spinning projectile, a 6.37-diameter long tangential-ogive-cylinder projectile is selected as the original model. Moreover, several boattail configurations are adopted to investigate the effects of boattail structures on the aerodynamics. Numerical simulations with the use of detached eddy simulation method have been performed to study the modification of boattail structure on the surface pressure of the projectile to expose the effects on the aerodynamic characteristics. The reliability of the numerical method has been validated through comparison with experimental data. The numerical results show that the variations of the wake vortex field due to the boattail structures have important influences on the surface pressure and the aerodynamic characteristics. The results provide important observations which can be valuable for design optimization of supersonic spinning projectile.

In the present work, unsteady effects present in a ship airwake are further analyzed. The effort is performed in the context of simulation of helicopter launch and recovery operations under a reali...

Turbulent combustion remains an unsolved problem, and the simulation models that have been developed, although accurate for subsonic turbulent combustion, have limited accuracy when applied to supe...

Boundary-layer-ingesting fans and compressors in the next-generation turbofan engines require high-performance operations under distorted inflow. The aim of this work is to study the effects of inlet distortions including inlet stagnation pressure and temperature distortion, on the aerodynamic performance of a transonic axial fan. Firstly, the validated full-annulus, unsteady, three-dimensional computational fluid dynamic code in conjunction with detached Eddy simulation approach is used here to simulate the fan flows assembly with individual inlet stagnation pressure/temperature distortion. Then, the propagation process of the inlet distortion waves is analyzed to understand how the aerodynamic performance degradation is triggered. The simulation results show that the fan performance is remarkably degraded when the inlet distortion is introduced. The leading-edge spillage, the trailing edge back flow and the “tornado vortex” occur when parts of fan blades encounter the incoming distorted flows. Finally, the responses of fan to the combined inlet stagnation distortion effects are discussed in this paper. It is found that the combined distortion effects can be predicted based on the sum of the performance responses to the individual constituent distortions. Furthermore, the relative location of the constituent distortions shows a non-ignorable influence on the overall fan performance, especially for the intensified inlet distortion.

This study investigates the influence of different pantograph parameters and train length on the aerodynamic drag of high-speed train by the delayed detached eddy simulation (DDES) method. The train geometry considered is the high-speed train with pantographs, and the different versions have 3, 5, 8, 10, 12, 16 and 17 cars. The numerical results are verified by the wind tunnel test with 3.6% difference. The influences of the number of cars and the position, quantity and configuration of pantographs on flow field around high-speed train and wake vortices are analyzed. The aerodynamic drag of middle cars gradually decreases along the flow direction. The aerodynamic drag of pantographs decreases with its backward shift, and that of the first pantograph decreases significantly. As the number of pantographs increases, its effect on the aerodynamic drag decrease of rear cars is more significant. The engineering application equation for the aerodynamic drag of high-speed train with pantographs is proposed. For the 10-car and 17-car train, the differences of total aerodynamic drag between the equation and the simulation results are 1.2% and 0.4%, respectively. The equation generalized in this study could well guide the design phase of high-speed train.

The current state of the use of large-eddy simulations (LESs) in jet aeroacoustics is reviewed. Various computational techniques are discussed, as well as methods to extend the LES results to the a...

International audience; Generating meshes with the right resolution is crucial for hybrid RANS/LES simulations of high Reynolds number flow with complex physical phenomena and geometries. This makes automatic mesh generation through adaptive refinement an interesting option. However, since the behavior of these turbulence models depends on the local grid size, mesh changes in time as a result of adaptive refinement may affect the production and destruction of turbulence. Therefore, grid adaptation with refinement criteria based on time-averaged quantities is proposed here to produce meshes that do not evolve rapidly in time and that are suitable for capturing the unsteady flow at each instant. Two averaging approaches, averaging over the instantaneous flow field, and averaging over the refinement criterion, are tested to simulate a turbulent flow behind a backward-facing step with a Detached Eddy Simulation type turbulence model. Compared to grid adaption based on instantaneous solutions, the computational cost is reduced, the accuracy of the solutions improves and an adapted mesh which has a generally static topology based on the main flow features is obtained. The investigation of this refinement process for two realistic test cases, a ship and a hybrid delta wing, confirms the reliability of the average-based adaptation and shows that automatic meshing for hybrid RANS/LES simulations of complex flows is possible.

This paper investigates the effects of different inlet velocity profiles on thermal mixing and conjugate heat transfer (CHT) within a T-junction. The flow domain is modelled using the Improved Delayed Detached Eddy Simulation (IDDES) turbulence model implemented within the commercial CFD software STAR-CCM+ 2020.1.1. The thermal analysis of the solid domain is also addressed within the CFD simulations. The OECD/NEA-Vattenfall experimental benchmark database is used to validate the CFD model. The effect of mesh sensitivity within the CFD simulations is also studied qualitatively and quantitatively. The influence of different inlet flow profiles on the CFD simulations is then assessed. Different combinations of inlet flow profiles, uniformly distributed and fully developed, are considered. Compared to the flow profile at the main pipe inlet, the flow profile at the branch pipe inlet presents a much more significant effect on the mean temperature distribution downstream of the T-junction. It is found that the flat flow profile at the branch inlet causes a higher temperature at the top wall, therefore a larger temperature gradient, and may lead to higher thermal stresses due to thermal stratification. The temperature distribution is more uniform for cases with the fully developed flow profile at the branch inlet. The variance of temperature is high at the sides of the pipe, regardless of the velocity profile used. The combination of flat flow profiles at both inlets causes the highest temperature variance. Moreover, the regions of maximum variance of temperature are located at different positions along the pipe section, depending on the combinations of inlet flow profiles.

Engine noise reduction using acoustic liner panels is an established technology in the design of bypass turbofan engines. Using acoustic impedance modeling techniques in aeroacoustic simulations, q...

Complex flow around floating structures is a highly nonlinear problem, and it is a typical feature in ship and ocean engineering. Traditional experimental methods and potential flow theory have limitations in predicting complex viscous flows. With the improvement of high-performance computing and the development of numerical techniques, computational fluid dynamics (CFD) has become increasingly powerful in predicting the complex viscous flow around floating structures. This paper reviews the recent progress in CFD techniques for numerical solutions of typical complex viscous flows in ship and ocean engineering. Applications to free-surface flows, breaking bow waves of high-speed ship, ship hull–propeller–rudder interaction, vortex-induced vibration of risers, vortex-induced motions of deep-draft platforms, and floating offshore wind turbines are discussed. Typical techniques, including volume of fluid for sharp interface, dynamic overset grid, detached eddy simulation, and fluid–structure coupling, are reviewed along with their applications. Some novel techniques, such as high-efficiency Cartesian grid method and GPU acceleration technique, are discussed in the last part as the future perspective for further enhancement of accuracy and efficiency for CFD simulations of complex flow in ship and ocean engineering.

This work introduces a fluidic oscillator design that allows control over the sweep and inclination angles, independent of the supply flow rate. These capabilities are made possible by injecting fl...

This paper uses an improved delayed detached eddy simulation method to investigate the unsteady flow features of the high-speed trains with various cavity lengths at Re = 1.85×106. The improved delayed detached eddy simulation results are validated against the experimental data obtained during previous wind tunnel tests. The effects of cavity length on the resistance force, flow structures beneath the high-speed train and in the wake are analyzed. The results show that a longer cavity significantly increases the streamwise velocity level near the rear plates and forms a stronger impinging flow on the rear plates, and thus contributes to a higher value of resistance. Furthermore, a longer cavity decreases the pressure coefficients around the near wake region from the top of the ballast to the tail nose in the vertical direction and thereby increases the pressure drag of the high-speed train. Additionally, a longer bogie cavity is found to increase the longitudinal vortex scales in the near wake region. All these changes on the flow field bring to 5.8% and 11.5% drag increase when the bogie cavities are elongated by 20% and 40%, respectively, of the wheelbase.

This study was conducted to investigate the impulsive acoustic characteristics of a lift-offset coaxial rotor in high-speed forward flight, as well as the impact of wake-grid resolution and turbule...

Dual-solver hybrid methodologies that couple fluid solvers in different regions of the flowfield have been developed to accelerate convergence with minimal compromises in accuracy. A new dual-solve...

The proposed passive control method, blade-end slots, is implemented to reorganize the blade-end flow in a highly loaded compressor cascade under a wide incidence range at Ma=0.59. Both experimenta...