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Uncontrolled proliferation of cells in a tissue caused by genetic mutations inside a cell is referred to as a tumor. A tumor which grows rapidly encounters a barrier when it grows to a certain size in presence of preexisting vasculature. This is the time when it has to find a way to go on the growth. The tumor starts to secrete tumor angiogenic factors (TAFs) and stimulate preexisting vessels to grow new sprouts. These new sprouts will find their way to the tumor in the extracellular matrix (ECM) by the gradient of TAF. As these new capillaries anastomose and reach tumor, fresh oxygen is available for the tumor and it will reinitiate the growth. Number of initial sprouts, distance of initial tumor cells from the vessel(s) and initial density of the tumor at the time of sprout formation are questions which are to be investigated. In the present study, the aim is to find the response of tumor cells and vessels to the reciprocal effects of each other in different circumstances in the tissue. Together with a mathematical formulation, a radial basis function (RBF) neural network is established to predict the number of tumor cells at different circumstances including size and distance of initial tumors from the parent vessel. A final formulation is given for the final number of tumor cells as a function of initial tumor size and distance between a parent vessel and a tumor. Results of this simulation demonstrate that, increasing the distance between a tumor and a parent vessel decreases the number of final tumor cells. Specially, this decrement becomes faster beyond a certain distance. Moreover, initial tumors in bigger domains must become much bigger before inducing angiogenesis which makes it harder for them to survive.

Deterministic lateral displacement (DLD) is a hydrodynamic method known for its high-resolution sorting of particles. It achieves this through a periodic array of obstacles and laminar flow that passively directs particles along in two different directions depending on the particles' diameter. Many prior publications have been dedicated to the structural and geometrical development of DLD arrays to improve separation performance; however, a successful separation requires much more than a well-designed array. This paper shows how separation performance is affected by process parameters. For this purpose, the design and fabrication of a DLD device are described. Then three experiments show how process parameters affect the performance of the device. The first experiment uses dye solutions to visualize the formation of a hydrodynamically focused sample stream. The second experiment shows that the particle separation performance (of 7-15-µm particles) is affected by the way output fluids are collected. Finally, the third experiment looks at the particle separation efficiency as the input flow rates and the ratio of buffer to sample are changed. The results show that the proper range for buffer and sample flow rate in this device is 1-10 and 0.1-1 (µl/min), respectively. The buffer to sample flow rate ratio of 10 gives the highest separation efficiency, but at a lower sample throughput. The optimized values are specific for our device but demonstrate processes that we believe are universal for DLD separations.

The vacuum degassing (VD) process is one of the prominent processes in the secondary metallurgy thereby improving the quality of the produced steel. The combination of steam ejectors and liquid-rin...

A finite element method with perturbation theory for calculating the secondary acoustic radiation force between cells and solid particles is implemented and simulated results were compared with experimental results. To do so, two sets of particles, including polystyrene particles...

In the present study, flow through two-dimensional microchannel under an axial electric field, transverse electric and magnetic fields and with axial pressure gradient has been investigated numerically. Continuity and momentum equations were solved steadily with respect to the non-slip condition by using discrete finite volume method and a numerical code. The results show that in the presence of the axial electric field, applying transverse magnetic field reduces flow velocity. However, when the transverse electric field and axial electric field exist together, applying the transverse magnetic field increases the flow rate to a certain extent and then reduces the flow rate. Hartmann number like this amount of magnetic field is known as critical Hartmann number. Therefore, with the presence of transverse and axial electric fields and transverse magnetic field, the highest possible flow rate is for critical Hartmann number. It was also found that by increasing the pressure gradient within the microchannel, the critical Hartmann number decreases. Moreover, by increasing the transverse electric field, the sensitivity of critical Hartmann number to the pressure gradient decreases and its value tends to a specific number (about 1.5).

Particulate separation has many applications in medicine, biology and industry. In this research, the separation of polystyrene particles with a diameter of 10, 20 and 30 μm in the fluid flow of a microchannel is investigated. The microchannel consists of a spiral region and a straight region under the influence of acoustic waves. In the spiral region, the particles under hydrodynamic effects undergo the initial separation; then the particles enter the straight region of the microchannel, and the final separation of the particles is done by the force generated and exerted through the acoustic waves. The effects of acoustic frequency and the number of spiral region loops on separation are investigated. The results show that for measured dimensions and parameters, at 1 MHz acoustic wave, when the number of loops is 2 for the spiral region, the particles at the end of the path are in a suitable position for separation. In addition, the results show that the separation of particles with this hybrid system is better than that done by the simple methods, and the separation rate can be as high as 100%

Since the effect of magnetic fields on blood flow is not fully understood or studied comprehensively, this paper, for the first time, addresses the effect of uniform magnetic fields with different intensities on the pulsatile non-Newtonian blood flow in an elastic artery with axially symmetrical single and double stenoses using the commercial software COMSOL Multiphysics 5.1. The results are suggestive that an increase in the percent stenosis increases the pressure drop, which is more dramatic in double stenosis. Moreover, for a given percent stenosis, increasing the Hartmann (Ha) number, in addition to increasing the pressure drop, increases the amount by which the pressure drop is raised. The shear stress results revealed that increasing the magnetic field intensity results in the reduction of the vortex region formed in the back of the stenosis, reducing the area prone to disease, which can resolve pathological issues. The impact of the magnetic field was found to be decreased by increasing the percent stenosis. It was also observed that the percentage difference between the maximum wall shear stresses for various percent stenoses is reduced by increasing the Ha number for both single and double stenoses.

We investigate cell-particle secondary acoustic radiation forces in a plain ultrasonic standing wave field inside a microfluidic channel. The effect of secondary acoustic radiation forces on biological cells is measured in a location between a pressure node and a pressure anti-node and the result is compared with theory by considering both compressibility and density dependent effects. The secondary acoustic force between motile red blood cells (RBCs) and MCF-7 cells and fixed 20 &micro, m silica beads is investigated in a half-wavelength wide microchannel actuated at 2 MHz ultrasonic frequency. Our study shows that the secondary acoustic force between cells in acoustofluidic devices could play an important role for cell separation, sorting, and trapping purposes. Our results also demonstrate the possibility to isolate individual cells at trapping positions provided by silica beads immobilized and adhered to the microchannel bottom. We conclude that during certain experimental conditions, the secondary acoustic force acting on biological cells can dominate over the primary acoustic radiation force, which could open up for new microscale acoustofluidic methods.

Intraperitoneal (IP) chemotherapy has revived hopes during the past few years for the management of peritoneal disseminations of digestive and gynecological cancers. Nevertheless, a poor drug penetration is one key drawback of IP chemotherapy since peritoneal neoplasms are notoriously resistant to drug penetration. Recent preclinical studies have focused on targeting the aberrant tumor microenvironment to improve intratumoral drug transport. However, tumor stroma targeting therapies have limited therapeutic windows and show variable outcomes across different cohort of patients. Therefore, the development of new strategies for improving the efficacy of IP chemotherapy is a certain need. In this work, we propose a new magnetically assisted strategy to elevate drug penetration into peritoneal tumor nodules and improve IP chemotherapy. A computational model was developed to assess the feasibility and predictability of the proposed active drug delivery method. The key tumor pathophysiology, including a spatially heterogeneous construct of leaky vasculature, nonfunctional lymphatics, and dense extracellular matrix (ECM), was reconstructed in silico. The transport of intraperitoneally injected magnetic nanoparticles (MNPs) inside tumors was simulated and compared with the transport of free cytotoxic agents. Our results on magnetically assisted delivery showed an order of magnitude increase in the final intratumoral concentration of drug-coated MNPs with respect to free cytotoxic agents. The intermediate MNPs with the radius range of 200–300 nm yield optimal magnetic drug targeting (MDT) performance in 5–10 mm tumors while the MDT performance remains essentially the same over a large particle radius range of 100–500 nm for a 1 mm radius small tumor. The success of MDT in larger tumors (5–10 mm in radius) was found to be markedly dependent on the choice of magnet strength and tumor-magnet distance while these two parameters were less of a concern in small tumors. We also validated in silico results against experimental results related to tumor interstitial hypertension, conventional IP chemoperfusion, and magnetically actuated movement of MNPs in excised tissue.

The aim is to study the assessment of the flow and convective heat transfer of laminar developing flow of Al2O3–water nanofluid inside a vertical tube. A finite volume method procedure on a structured grid was used to solve the governing partial differential equations. The adopted model (Buongiorno model) assumes that the nanofluid is a mixture of a base fluid and nanoparticles, with the relative motion caused by Brownian motion and thermophoretic diffusion. The results showed the distribution of nanoparticles remained almost uniform except in a region near the hot wall where nanoparticles volume fraction were reduced as a result of thermophoresis. The simulation results also indicated there is an optimal volume fraction about 1–2% of the nanoparticles at each Reynolds number for which the maximum performance evaluation criteria can be obtained. The difference between Nusselt number and nondimensional pressure drop calculated based on two phase model and the one calculated based on single phase model was less than 5% at all nanoparticles volume fractions and can be neglected. In natural convection, for 4% of nanoparticles volume fraction, in Gr = 10 more than 15% enhancement of Nusselt number was achieved but in Gr = 300 it was less than 1%.

Atherosclerosis develops due to different hemodynamic factors, among which time-averaged Wall shear stress (mean WSS) and Oscillatory shear index (OSI) are two of the most important. These two factors not only depend on flow geometry, but are also influenced by rheological characteristics of blood. Since analytical solutions are limited to simple problems and since experimental tests are costly and time consuming, CFD solutions been prominently and effectively used to solve such problems. We conducted a numerical study via ADINA 8.8 software on the non-Newtonian pulsatile flow of blood through an elastic blood artery with single and consecutive stenosis. The studied stenosis cross sectional area was 70 % that of the unstenosed artery. The single stenosis results were compared with the consecutive stenosis results. The five non-Newtonian flow models, the Carreau model, the Carreau-Yasuda model, the modified Casson model, the power-law model, and the generalized power-law model, were used to model the non-Newtonian blood flow. The obtained results showed that increasing the number of stenoses would lead to reduced length of the oscillatory area after the first stenosis, thus forming another oscillatory area with a larger length after the second stenosis. Thus, a consecutive stenosis would develop a larger disease prone area. Upon examining the mean WSS and OSI, we found that, as compared with the other models, the modified Casson model and the power-law model produced predictions for the most extent of damage to endothelial cells and the most disease prone areas, respectively.

The objective of the present study is to investigate experimentally the non-homogenous distribution of nanoparticles in the nanofluid by natural convection heat transfer inside a square enclosure. There are some phenomenon such as fluid motion, Brownian effect, thermophoresis effect and gravity which cause nanoparticles movements throughout the nanofluid. An experimental set-up was built to carefully take micro-litter samples of nanofluid from a 8 × 8 × 18 (cm3) square cavity. The nanofluid was prepared using 20 nm-gamma type Al2O3 nanoparticles dispersed in deionized distilled water. The experiments were done for three Rayleigh numbers 0.992 × 107, 0.51 × 108 and 1.53 × 108 and the particle loading of 1% was constant during the experiments. The contours of nanoparticle fraction shows that the assumption of non-homogeneity is correct and the regions of high and low nanoparticle volume concentration are distinguishable. The fluid motion is the most important factor that may come in to play especially at higher Rayleigh number and causes the maximum differences between measured nanoparticle concentration. The result showed that the differences between maximum and minimum volume fraction in the whole cavity increases from 18% at Ra = 0.992 × 107 to 28.74% at Ra = 1.51 × 108. It was observed that the average nanoparticle volume fraction along cold wall is 3.10% greater than that along hot wall for minimum Ra number however at higher Ra numbers this difference would weaken. To check precision of replicates and ensure accuracy, the data were analyzed using analysis of variance method (ANOVA method). The present work reveals that there are still some issues for flow and thermal mechanisms in nanofluids, particularly regarding the nanoparticles distribution for future works.

Objectives The aim of this study was to investigate the response of a tumor and parent vessels to stimulating factors in the tumor microenvironment in different configurations. How a tumor grows and induces angiogenesis in different distances of a parent vessel is investigated. Moreover, interstitial fluid pressure and its effects on tumor cell phenotype are considered in the model. Methods A multiscale continuum-discrete model of a vascular tumor is utilized to simulate the growth of a cluster of tumor cells positioned in different distances of parent vessels. An agent-based probabilistic angiogenesis model is coupled to a discrete tumor model to simulate branching, anastomosis, blood flow, wall shear stress, and interstitial tumor pressure in which tumor cells are divided to necrotic, hypoxic, and proliferative. Results Starting the simulations from 9 initial tumor cells, the model proved that tumors grow to a certain size and also reach to a certain distance before being able to induce sprouting. For tumors placed 2 and 2.5 mm away from a parent vessel, initiation of angiogenesis is delayed significantly in comparison with closer distances. For the initial cluster positioned in a distance of 2.5 mm away, first sprout is seen after 47 days. Moreover, dendritic shape of the tumor is seen prior to angiogenesis which is a sign of cells being starved and wandered in the domain to reach the oxygen source. The trend of tumor growth obeys power law function which aligns with the experimental results. Discussion The mathematical model revealed the importance of geometry and position of an initial tumor cluster in determining the behavior and final architecture of a vascular tumor. As a tumor cell appears in farther distances from a parent vessel, duration of its growth and inducing angiogenesis becomes longer and the chance of suppressing the tumor in the initial days of growth is higher. Also, the importance of angiogenesis in making tumors devastating is again corroborated by mathematical models.

A method is presented for measurements of secondary acoustic radiation forces acting on solid particles in a plain ultrasonic standing wave. The method allows for measurements of acoustic interaction forces between particles located in arbitrary positions such as in between a pressure node and a pressure antinode. By utilizing a model that considers both density- and compressibility-dependent effects, the observed particle−particle interaction dynamics can be well understood. Two differently sized polystyrene micro-particles (4.8 and 25 μm, respectively) were used in order to achieve pronounced interaction effects. The particulate was subjected to a 2-MHz ultrasonic standing wave in a microfluidic channel, such as commonly used for acoustophoresis. Observation of deflections in the particle pathways shows that the particle interaction force is not negligible under this circumstance and has to be considered in accurate particle manipulation applications. The effect is primarily pronounced when the distance between two particles is small, the sizes of the particles are different, and the acoustic properties of the particles are different relative to the media. As predicted by theory, the authors also observe that the interaction forces are affected by the angle between the inter-particle centerline and the axis of the standing wave propagation direction.

In this paper, the effects of both constant and alternating magnetic fields on the laminar forced convective heat transfer of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe 3 O 4 nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs) flowing through a heated tube were investigated experimentally. The experiments were carried out over wide range of parameters such as Reynolds number (548–2190), volume concentrations of Fe 3 O 4 (0.5–0.9%) and carbon nanotube (0.25–1.35%) nanoparticles, magnetic field strength (300–700 Gauss) and alternating magnetic field frequency (10–50 Hz). In present study, the experimental observations in the case without magnetic field revealed that by using Fe 3 O 4 /CNT hybrid nanofluid, the convective heat transfer has been improved significantly. The maximum enhancement of 62.7% was achieved in the local Nusselt number for hybrid nanofluid containing 0.5 vol.% Fe 3 O 4 and 1.35 vol.% CNT at Reynolds number equals to 2190. Additionally, the results showed that the heat transfer of the studied hybrid nanofluids has been improved in the presence of constant and alternating magnetic fields and the amount of heat transfer increment due to a constant magnetic field was much more significant compared with an alternating magnetic field. Moreover, the effects of magnetic field were more noticeable in the hybrid nanofluids with higher volume concentrations and lower Reynolds number. Eventually, the highest increment of 20.5% in comparison with the case without field was reported in the local Nusselt number for hybrid nanofluid containing 0.5 vol.% Fe 3 O 4 and 1.35 vol.% CNT at Reynolds number equals to 548.

Natural convection heat transfer within horizontal annuli has many engineering applications such as heat exchangers like fire tube heaters. In this paper numerical methods were used for the computational analysis of heat transfer from the fire tube/hot tube to the gas tube/cold tube inside the water medium using alumina nanoparticles. Because of eccentricities of both hot and cold cylinders and different diameters, the geometry is asymmetric. The mathematical model is based on two-dimensional continuity, momentum, energy, and volume fraction equations, which are solved numerically. The simulation was done for different values of particle loading, 1%, 2%, and 5%, at Rayleigh numbers 103, 104, and 105. The results show that nanoparticles enhance the heat transfer by increasing the volume concentrations of particles. It was observed that the maximum and minimum augmentation of the average Nusselt number are about 30% and 14% at the Ra = 103 and Ra = 105, respectively. Although the average Nusselt num...

Journal bearings are widely used in different machineries. Reynolds equation is the governing equation to predict pressure distribution and load bearing capacity in journal bearings. There are many analytical and numerical methods for solving this equation. The main disadvantage of these methods is their inability to analyze complex geometries. In this paper, a comprehensive method based on dynamic mesh method is developed to solve the conservation equations of mass, momentum and energy. This method has smaller error compared to other techniques. To verify the accuracy of this method, the bearings with different length to diameter ratios are analytically and numerically analyzed under different loads and compared with each other. In continue, the turbocharger’s bearing is numerically simulated and the effects of rotational speed change are studied. Finally, the turbocharger’s bearing with four axial grooves are simulated. The simulations results show that adding grooves to the turbocharger’s bearing causes the bearing eccentricity ratio and lubricant flow rate to increase and the attitude angle, rate of temperature rise and frictional torque to decrease.

The lift to drag ratio is the most determining factor in power efficiency of wind conversion systems such as wind turbines. The lift to drag ratio can be enhanced considerably using circulating airfoil shapes. In this research, the NACA0021 airfoil is modified and manufactured to form a treadmill like circulating shape. Aerodynamic performance of the treadmill shape is computationally and experimentally investigated. In the experiment, the smoke flow visualization is conducted in a small wind tunnel to study flow features such as separation and stagnation points. Computational method is based on the finite volume discretization of RANS (Reynolds Averaged Navier–Stokes) equations and the shear stress transport (k–ω SST (shear-stress transport)) turbulence modeling. Magnus effects are investigated under various speed ratios (speed of circulating surface to the wind speed) and several angles of attack. The numerical and flow visualization results reveal some main changes to flow features including full removal of separation zone above moving surfaces. At the speed ratio of 3, zero angle of attack and flow Reynolds number of 94,000, an impressive lift to drag ratio of 130 is obtained for the circulating airfoil whilst the maximum attainable value is merely 45 for the original NACA0021 airfoil.

The present work examines experimentally the effect of magnetic field on the viscosity and thermal conductivity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and Gum arabic (GA) coated carbon nanotubes (CNTs). The hybrid nanofluid was prepared by using ultrasonic dispersion method. Magnetic field was created by a pair of spaced apart magnet plates. The effect of temperature on the time variation of thermal conductivity under applied magnetic field was also investigated. According to the results of this study, viscosity of the hybrid nanofluid increases with the strength of magnetic field, while it decreases with the increase of temperature. Additionally, it is found that the hybrid nanofluid behaves as a shear thinning fluid at low shear rates while it exhibits Newtonian behavior at high shear rates. Furthermore, results show that when an external magnetic field is applied to the studied magnetic nanofluids, the thermal conductivity experiences a peak.

The aim of this paper is to investigate the thermal conductivity and viscosity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs), experimentally. The magnetic nanoparticles and CNTs are physically attached as the result of interaction between the TMAH and GA molecules. The morphology and structure of the samples are characterized with X-ray diffraction (XRD) and transmission electron microscopy (TEM). The experiments are carried out in the magnetic nanoparticles volume concentration range of 0.1–0.9 %, CNT volume concentration range of 0.05–1.35 % and the temperature range of 25–55 °C. The viscosity of the hybrid nanofluid increases with the increase of volume concentration, while it decreases with the increase of temperature. Besides, results show that hybrid nanofluid behaves as a shear thinning fluid. Furthermore, it is observed that the thermal conductivity of the hybrid nanofluid enhances with temperature and volume concentration.

Developing steady laminar flow and mixed convection heat transfer of a Newtonian conducting fluid in an open-ended vertical parallel plate microchannel under the effect of a uniform magnetic field are numerically studied. The effects of the modified mixed convection parameter, \(\frac{{Gr}} {{Re}}\), the Hartmann number, M, the Knudsen number, Kn, and the heat flux ratio, rq, on the velocity and temperature profile are investigated. It is revealed that the velocity profile is strongly influenced by magnetic field. In fact, with an increase in the Hartmann number the velocity decreases for both Kn = 0 and 0.1 and for all mixed convection parameter values. The effect of magnetic force on the velocity profile is stronger, with respect to the temperature profile. In addition, with an increase in M, the slip velocity increases on both hot and cold walls for rq = 0 and rq = 1. It is observed that the friction factor coefficient has significant increases with an increase in the Hartmann number.

Tumor cells are known for their increased glucose uptake rates even in the presence of abundant oxygen. This altered metabolic shift towards aerobic glycolysis is known as the Warburg effect. Despite an enormous number of studies conducted on the causes and consequences of this phenomenon, little is known about how the Warburg effect affects tumor growth and progression. We developed a multi-scale computational model to explore the detailed effects of glucose metabolism of cancer cells on tumorigenesis behavior in a tumor microenvironment. Despite glycolytic tumors, the growth of non-glycolytic tumor is dependent on a congruous morphology without markedly interfering with glucose and acid concentrations of the tumor microenvironment. Upregulated glucose metabolism helped to retain oxygen levels above the hypoxic limit during early tumor growth, and thus obviated the need for neo-vasculature recruitment. Importantly, simulating growth of tumors within a range of glucose uptake rates showed that there exists a spectrum of glucose uptake rates within which the tumor is most aggressive, i.e. it can exert maximal acidic stress on its microenvironment and most efficiently compete for glucose supplies. Moreover, within the same spectrum, the tumor could grow to invasive morphologies while its size did not markedly shrink.

Nanofluids containing Fe 3 O 4 and carbon nanotubes nanoparticles emulsified and dispersed using gum arabic (GA) and tetramethylammonium hydroxide (TMAH) were made and characterized for potential use as heat transfer fluids. Due to the interaction between the TMAH and GA molecules, the magnetic nanoparticles and CNTs were physically adsorbed. This paper reports an experimental work on the effect of ultrasonication on thermal conductivity of this aqueous suspension. The characterization and surface morphology of the dried samples were studied by using XRD and TEM measurements. Experiments were conducted in the magnetic nanoparticles mass concentration range 0.494–2.428%, CNT mass concentration range 0.0–1.535% and the temperature range 25–55 °C. Results show that thermal conductivity of the studied nanofluids is affected by ultrasonication time, increased first and then decreased after an optimum sonication time. Additionally, results show that addition of GA coated CNT nanofluid increases the thermal conductivity of the aqueous nanofluid containing TMAH coated Fe 3 O 4 nanoparticles.

This article investigates the pulsatile and turbulent blood flows in flexible artery with single and double stenoses. The changes in pressure drop, mean wall shear stress (WSS), radial displacement of the artery, and oscillating shear index are investigated. Similar to experimental data, the results of the present study show that a laminar flow occurs for stenosis of up to 70%, and for 80% stenosis the flow is turbulent. The mean WSS analysis shows that assuming the flow is laminar causes more errors than assuming the walls are solid. The comparison of the results for single stenosis with those for double stenosis reveals that the dilation in the arterial walls in double stenoses is much more common than in single stenosis. Therefore, the maximum mean WSS in double stenoses is less than that in single stenosis. The results also indicate that the axial pressure drop in double stenoses is higher than that in single stenosis.

Research on the development and incidence of cardiovascular diseases has revealed the importance of vascular wall shear stress. In this paper, the vascular wall shear stress was numerically simulated in an elastic vessel with simple and consecutive Stenosis during a pulsatile laminar non-Newtonian blood flow using ADINA 8.8. The cross-sectional area of the studied stenosis was 70% of the unstenosed vascular cross-sectional area. The results of the simple stenosis were compared with those of the double stenosis. Five non-Newtonian models of Carreau, Carreau-Yasuda, Casson, Power Law, and Generalized Power Law were employed to simulate the non-Newtonian properties of blood. The axial velocity values at the maximum flow rate showed that in both simple and consecutive Stenosis, the highest and lowest axial velocities occur in the Generalized Power Law and Power Law models, respectively. Wall shear stress profiles at the maximum flow rate showed that the Power Law model underestimates the stress values compared to other non-Newtonian models and the Newtonian model. In general, results showed that the Power Law model is not suitable for simulating the non-Newtonian behavior of blood.

Emerging evidence shows that endothelial cells are not only the building blocks of vascular networks that enable oxygen and nutrient delivery throughout a tissue but also serve as a rich resource of angiocrine factors. Endothelial cells play key roles in determining cancer progression and response to anti-cancer drugs. Furthermore, the endothelium-specific deposition of extracellular matrix is a key modulator of the availability of angiocrine factors to both stromal and cancer cells. Considering tumor vascular network as a decisive factor in cancer pathogenesis and treatment response, these networks need to be an inseparable component of cancer models. Both computational and in vitro experimental models have been extensively developed to model tumor-endothelium interactions. While informative, they have been developed in different communities and do not yet represent a comprehensive platform. In this review, we overview the necessity of incorporating vascular networks for both in vitro and in silico cancer models and discuss recent progresses and challenges of in vitro experimental microfluidic cancer vasculature-on-chip systems and their in silico counterparts. We further highlight how these two approaches can merge together with the aim of presenting a predictive combinatorial platform for studying cancer pathogenesis and testing the efficacy of single or multi-drug therapeutics for cancer treatment.

The linear stability based on Orr-Sommerfeld equations and the eN method was employed to determine the onset and control of transition over VFW-VF-2 and NACA653-018 aerofoil sections. For the VFW-VF-2 aerofoil, the effects of active suction on shock-boundary layer interaction were investigated. An enhanced lift to drag ratio was obtained for incidence angles below 6 degrees using suction coefficient as tiny as 0.0006. A parametric study were conducted to show the effects of the suction slot location, suction inclination angle and the extent of sucked flow through slots for flows around the NACA653-018 aerofoil. It was observed that transition was delayed regardless of suction positions. However, maximum delay in transition occurred when the sucked region was located between a critical point and the transition point. For all the cases studied here, lift to drag ratio was increased using active surface suction.

The performance of the multigrid method and the effect of different grid levels on the convergence rate are evaluated. The two-, three-, and four-level V-cycle multigrid methods with the Gauss-Seidel iterative solver are employed for this purpose. The numerical solution of the one-dimensional Laplace equation with the Dirichlet boundary conditions is obtained using these methods. For the Laplace equation, a two-frequency function involving high- and low-frequency components is defined. It is observed that, however, the GS method can smooth out the high-frequency error components properly, but because the difference scheme for Laplace equation is remarkably concise, in the fine grids, a very large number of iterations are needed for extending the boundary conditions into the domain. Furthermore, the obtained results reveal that the number of necessary iterations for convergence is reduced considerably by employing the two-level multigrid algorithm. But increasing the number of levels of algorithm does not have any significant effect on the convergence rate in this study.

Forced convection heat transfer from two and three isothermal circular cylinders in tandem arrangement is studied numerically. In addition, the flow field and the vortex shedding behavior in the wake of the cylinders are investigated. The governing equations consist of continuity, momentum and energy equations are solved for laminar unsteady flow regime. The numerical simulations are performed with a developed finite volume code using the overset grid method. A general orthogonal boundary fitted coordinate system is used for the grid generation. This simulation is performed for the Prandtl numbers of 0.7 and 7 at the Reynolds numbers of 100 and 200. The spacing ratio L/D is set at 2, 3, 4, 5, 7 and 10. In order to analyze the heat transfer from isothermal cylinders, the mean and local Nusselt numbers and isotherm plots are presented and discussed for different values of the problem parameters. In addition, the mean and instantaneous drag and lift coefficients and Strouhal numbers are computed to elucidate the role of the Reynolds number and spacing ratio. Furthermore, two new correlations for the calculation of the mean Nusselt number, in terms of the spacing ratio and the Reynolds and Prandtl numbers, is proposed. In order to validate the solution, the obtained results are compared with available results in the published literature.

The problem of imposing an in-line velocity perturbation on a uniform flow about a fixed cylinder is studied numerically. A finite volume method using SIMPLEC algorithm is applied on an O-type body-fitted co-located grid. The effect of frequency, amplitude, and shape of the velocity perturbation on the lift and drag coefficients and the Nusselt and Strouhal numbers were studied for the case of Reynolds number equal to 1000. It is noticed that lock-on is present and have a pronounced effect on the average Nusselt number, increasing it by 8.3 percent relative to the uniform flow value, though with a lower effect on drag and lift coefficients. In addition, it is concluded that a sinusoidal perturbation with a dimensionless frequency equal to 0.15 and dimensionless velocity perturbation equal to 0.2 is a better choice to enhance the heat transfer rate.

Steady incident flow past a circular cylinder for sub- to supercritical Reynolds number has been simulated as an unsteady Reynolds-averaged Navier–Stokes (RANS) equation problem using nonlinear eddy-viscosity modelling assuming two-dimensional flow. The model of Craft et al. (Int. J. Heat Fluid Flow 17 (1996) 108), with adjustment of the coefficients of the ‘cubic’ terms, predicts the drag crisis at a Reynolds number of about 2×105 due to the onset of turbulence upstream of separation and associated changes in Strouhal number and separation positions. Slightly above this value, at critical Reynolds numbers, drag is overestimated because attached separation bubbles are not simulated. These do not occur at supercritical Reynolds numbers and drag coefficient, Strouhal number and separation positions are in approximate agreement with experimental measurements (which show considerable scatter). Fluctuating lift predictions are similar to sectional values measured experimentally for subcritical Reynolds numbers but corresponding measurements have not been made at supercritical Reynolds numbers. For oscillatory ambient flow, in-line forces, as defined by drag and inertia coefficients, have been compared with the experimental values of Sarpkaya (J. Fluid Mech. 165 (1986) 61) for values of the frequency parameter, β=D2/νT, equal to 1035 and 11240 and Keulegan–Carpenter numbers, KC=U0T/D, between 0.2 and 15 (D is cylinder diameter, ν is kinematic viscosity, T is oscillation period, and U0 is the amplitude of oscillating velocity). Variations with KC are qualitatively reproduced and magnitudes show best agreement when there is separation with a large-scale wake, for which the turbulence model is intended. Lift coefficients, frequency and transverse vortex shedding patterns for β=1035 are consistent with available experimental information for β≈250−500. For β=11240, it is predicted that separation is delayed due to more prominent turbulence effects, reducing drag and lift coefficients and causing the wake to be more in line with the flow direction than transverse to it. While these oscillatory flows are highly complex, attached separation bubbles are unlikely and the flows probably two dimensional.

The turbulent pulsatile blood flow through stenosed arteries considering the elastic property of the wall is investigated numerically. During the numerical model validation both standardk-εmodel and RNGK-εmodel are used. Compared with the RNGK-εmodel, the standardK-εmodel shows better agreement with previous experimental results and is better able to show the reverse flow region. Also, compared with experimental data, the results show that, up to 70% stenosis, the flow is laminar and for 80% stenosis the flow becomes turbulent. Assuming laminar or turbulent flow and also rigid or elastic walls, the results are compared with each other. The investigation of time-averaged shear stress and the oscillatory shear index for 80% stenosis show that assuming laminar flow will cause more error than assuming a rigid wall. The results also show that, in turbulent flow compared with laminar flow, the importance of assuming a flexible artery wall is more than assuming a rigid artery wall.

In this numerical study, flow-induced vibrations of a heated elastically supported cylinder in a laminar flow with Re = 200 and Pr = 0.7 are simulated using the moving overset grids method. This work is carried out for a wide range of natural frequencies of the cylinder, while for all cases mass ratio and reduced damping coefficient, respectively, are set to 1 and 0.01. Here we study lock-in condition and its effects on force coefficients, the amplitude of oscillations, vortex shedding pattern, and Nusselt number and simultaneously investigate the effect of in-line oscillations of the cylinder on these parameters. Results show that for this cylinder, soft lock-in occurs for a range of natural frequencies and parameters like Nusselt number, and the amplitude of oscillation reach their maximum values in this range. In addition, this study shows that in-line oscillations of the cylinder have an important effect on its dynamic and thermal behavior, and one-degree-of-freedom simulation, for an elastic cylinder, which can vibrate freely in a flow field, is only valid for cases far from soft lock-in range.

One of the development parameters of each country is the accessibility of its different regions to energy resources, especially electrical energy. Therefore, construction of new power plants is inevitable. Nevertheless, limited fossil fuel energy resources and environmental pollutant emissions further proves the necessity toward renewable energy use. To overcome intermittent nature of renewable energies such as solar and wind, development of hybrid energy systems has been proposed. In this study, the feasibility of wind and solar renewable energies was investigated for Khorramabad city as an example of a city in a developing country using HOMER (hybrid optimization model for electric renewable) software. First, data for wind and solar energies were collected from renewable energy organization of Iran. Second, Geographic Information System (GIS) maps were plotted for solar and wind energies of the country and Lorestan Province where the city of Khorramabad is located. Third for Khorramabad city, the amount of electricity generated by wind, solar, and fuel cell sources were investigated in different months of a year, the contribution of each unit in costs, the amount of costs associated to different power plants, and the amount of pollutant emissions from fuel cell using HOMER. The results indicate that the use of fuel-cell system is not recommended for Khorramabad or similar cities in developing countries due to low performance and high initial costs. On the other hand, using a combined system of wind energy, solar energy, and diesel generator will be economical and is recommended.

Flowtransition from laminar toturbulent is prerequisite todecide whereabouts to apply surface flowcontrol techniques. This appears missing in a number of works in which thecontrol effects were merelyinvestigated without getting insight into alteration of transition position. The aim of this study is to capture the correctposition of transition overNACA0012 aerofoil at different angles of attack. Firstly, an implicit, time marching, highresolution total variation diminishing (TVD) scheme was developed to solve the governingNavier—Stokes equations forcompressible fluid flows around aerofoil sections to obtain velocity profiles around the aerofoilsurfaces. Secondly, the linear instability solver based on the Orr—Sommerfeld equations and the eN methods were developed to calculate the onset of transition over the aerofoil surfaces. Forthe low subsonic Mach number of 0.16, the accuracy of the compressible solutions was assessed bysome available experimental results of low speed incompressible flows. In allcases, transition positionswere accurately predicted which shows applicability and superiority of the present work to beextended for higher Mach number compressible flows. Here, transition prediction methodology is described and the results of this analysiswithout active flow controlor separation are presented.