Fluid Flow Analysis Research Articles

Application of Michell’s Integral to High-Speed Round-Bilge Hull Forms

Computational fluid dynamics (CFD) techniques are becoming increasingly popular in analyzing fluid flow problems in almost all branches of engineering, especially in resistance prediction of ships where complex fluid flow exists, although absolute accuracy is still limited. Application of CFD techniques in resistance prediction of ships is no longer new and is being enthusiastically embraced by researchers as can be seen from articles in journals and conference proceedings. Although the towing tank tests provide better absolute accuracy, modification to hull forms is limited, resulting from both practical and financial constraints. In this respect, CFD techniques and theoretical formulations have an added advantage in the sense that rapid modifications to hull forms can be carried out and results can be obtained, so that a comparative study could be made within a few hours. In this way, a naval architect is in a better position to select a hydrodynamically efficient design. Furthermore, robust and fast hydrodynamic computational methods are essential elements of advanced numerical optimization techniques. A good high-speed design should have favorable resistance qualities, so that operational capabilities are not degraded. Innumerable investigations available in the literature enumerate resistance prediction of systematic series of high-speed hull forms. In this article, the results of a comparative study on resistance of high-speed round-bilge hull forms using CFD techniques, theoretical analysis, and experimental results have been presented. The need for better hull forms and the increased interest in resistance performance call for better data and efficient algorithms to be available at the design and optimization stage to obtain the right balance between resistance and other conflicting requirements. This article provides a study of the following. The result of modeling in SHIPFLOW, which uses a combined potential-flow boundary-layer viscous-flow zonal approach. Application of a fast resistance estimation method with the wave-making resistance by Michell’s integral, the friction resistance by International Towing Tank Conference 1957. Application of Michell’s integral to determine the wave resistance of the systematic series models. Comparison between the total resistance coefficients obtained from experimental work, SHPFLOW, and the fast resistance estimation method.

Flow and heat transfer analysis of Eyring-Powell fluid over stratified sheet with mixed convection

This article presents the study of heat transfer under the influence of mixed convective flow of Eyring-Powell fluid over a stratified stretching sheet. The impact of heat generation/absorption is also discussed. The fluid is considered to be a viscous, incompressible, two dimensional, and laminar. Transformation, based on the similarity variables, is used for the alteration of modeled governing partial differential equations (PDEs) into ordinary differential equations (ODEs). The shooting approach is introduced to accomplish the mathematical solution of governing equations. Runge-Kutta method of order four is used for the integration purpose and Newton’s method helps to refine initial guesses. All the programming is done on MATLAB. The effects of emerging parameters on temperature and velocity profiles are discussed through graphs. The related physical properties of flow, i.e., the skin friction coefficient and Nusselt number are described graphically for various parameters. Numerical values for the Nusselt number and skin friction coefficient are tabulated for the various parameters. It is noted that increment in thermal stratification parameter yields fall in both velocity and temperature of fluid and a reverse relation is observed for the heat generation parameter.

Computational fluid dynamics analysis of mixing and gas-liquid mass transfer in wave bag bioreactor.

Single use bioreactors provide an attractive alternative to traditional deep-tank stainless steel bioreactors in process development and more recently manufacturing process. Wave bag bioreactors, in particular, have shown potential applications for cultivation of shear sensitive human and animal cells. However, the lack of knowledge about the complex fluid flow environment prevailing in wave bag bioreactors has so far hampered the development of a scientific rationale for their scale up. In this study, we use computational fluid dynamics (CFD) to investigate the details of the flow field in a 20-L wave bag bioreactor as a function of rocking angle and rocking speed. The results are presented in terms of local and mean velocities, mixing, and energy dissipation rates, which are used to create a process engineering framework for the scale-up of wave bag bioreactors. Proof-of-concept analysis of mixing and fluid flow in the 20-L wave bag bioreactor demonstrates the applicability of the CFD methodology and the temporal and spatial energy dissipation rates integrated and averaged over the liquid volume in the bag provide the means to correlate experimental volumetric oxygen transfer rates (kL a) data with power per unit volume. This correlation could be used as a rule of thumb for scaling up and down the wave bag bioreactors.

Numerical analysis of MHD casson fluid flow over an exponentially accelerated vertical plate in embedded porous medium with ramped wall temperature and ramped surface concentration in uniform magnetic field

<div data-canvas-width="162.73488208022576">Numerical analysis of MHD casson fluid flow over an exponentially accelerated vertical plate in embedded porous medium with ramped wall temperature and ramped surface concentration has investigated in the current investigation. The flow governing dimensional velocity, temperature and concentration differential equations are converted into non dimensional form by using non-dimensional variables. Numerical solutions to the converted equations are obtained by finite element method. The results are presented graphically and in tabular form for various controlling parameters. In order to highlig ht the validity and accuracy of our present method, we have compared our results with the results obtained earlier. A very good validation of the present numerical results has been achieved</div><div>.</div>

Analysis of immiscible Newtonian and non-Newtonian micropolar fluid flow through porous cylindrical pipe enclosing a cavity

In the considered problem, we presented a model for the flow of immiscible fluids (non-Newtonian and Newtonian) through the cylindrical pipe. Cylindrical pipe is constituted by two porous cylindrical shell enclosing a cylindrical cavity. Non-Newtonian (micropolar) fluid is flowing through the middle porous cylindrical shell, and other immiscible Newtonian fluids are flowing through the cavity and outer porous cylindrical shell. The flow of fluid through the outer porous cylindrical shell and cavity is governed by well-known Brinkman and Stoke’s equation, respectively. However, the flow of micropolar fluid through the middle porous cylindrical shell is governed by the field equation given by Eringen (Springer, Berlin, 2001). An analytical solution of the problem has been obtained by using the justified boundary conditions. The effects of various non-dimensional parameters such as permeability parameters, micropolar parameter, and viscosity ratio on the linear flow velocity, microrotational flow velocity and flow rate are examined graphically. The results are validated with the help of previously established result.

Numerical analysis of MHD casson fluid flow over an exponentially accelerated vertical plate in embedded porous medium with ramped wall temperature and ramped surface concentration in uniform magnetic field

Numerical analysis of MHD casson fluid flow over an exponentially accelerated vertical plate in embedded porous medium with ramped wall temperature and ramped surface concentration in uniform magnetic field

Better Natural Ventilation Design for Single Sided Apartments Utilising Computational Fluid Dynamics

Wind-driven natural cross ventilation to many single-aspect apartments can be achieved via building indentations and façade articulation. The ventilation rate of these apartments will rely on pressures differences between openings caused by approaching wind pressure, local wind climate and interaction with the surrounding built environment and external pressure gradients on the building indentations or any other facades articulation and their potential driving force on natural ventilation. Detailed simulation methods are therefore required to consider all above mentioned parameters and provide internal and external airflow information to the design team to allow for design modifications or refinement where required to provide robust natural cross ventilation for such apartments. This study assesses the above parameters for a proposed development, designed with recesses and slots to enhance natural cross ventilation in single-sided apartments, and presents a reliable procedure to advise on compliance with national and/or international design guidelines utilising an advanced combined outdoor-indoor Computational Fluid Flow (CFD) analysis integrated with localized weather data for the project site.

Infill well wellbore stability analysis by considering plasticity, stress arching, lateral deformation and inhomogeneous depletion of the reservoir

The traditional way of analyzing wellbore stability of infill wells relies on the analytical solution of the stress path, which assumes uniaxial strain, homogenous depletion, constant overburden stress, and linear elastic condition. The objective of this study is to re-evaluate all the above four assumptions and analyze the plasticity, stress arching, lateral deformation and inhomogeneous depletion of the reservoir. Coupled geomechanics and fluid flow analysis is conducted to get the time and location dependent stress field and pressure field, which serve as inputs for wellbore stability analysis for infill wells. Considering four cases, the ranking according to the width of the safe drilling mud weight windows is 1) plasticity, 2) elasticity, 3) plasticity with stress arching, and 4) elasticity with stress arching. This coupled geomechanics and fluid flow can provide dynamic information concerning where to drill, when to drill, and how to drill for infill wells.

Numerical and experimental thermal performance with entropy generation analysis on tube with helical screw tape inserts at number of strips in turbulent flow

In the heat exchangers, twisted tape insert is a technique to enhance heat transfer. In this paper, the experimental and numerical investigations are arranged to analyze thermal performance with entropy generation analysis on single and double strip helical screw tape inserts. The finite volume method is used with shear stress transport K-ω model to analyze fluid flow in tube with inserts. The Nusselt number attained enhancement with double strip as compared to single strip helical screw inserts at decreased values of twist ratio and increased values of Reynolds number. However, the Nusselt number attained maximum enhancement of 112% with double strip helical screw insert than plain tube at 4000 of Reynolds number (Re). The common correlations for Nusselt number and friction factor are generated with respect to Reynolds number, number of the strips and twist ratio. Entropy generation analysis is also performed. The thermal performance factor attained its enhancement with double strip than single strip helical screw inserts at twist ratio of 2.5 and 3; whereas, double strip helical screw insert attained maximum value of 1.5 at twist ratio of 2.5 and Reynolds number of 16000. The double strip helical screw inserts are suitable for miniaturization of heat exchanger.

Temperature Analysis of Wet Clutch Surfaces During Clutch Engagement Processes Based on Friction Pad Patterns

Temperature distributions of wet clutch contact during engagement and disengagement processes are investigated considering lubricant flow behaviors in the gap between the friction pad and steel separator. Frictional heat generated by wet clutch contact in repeated operational modes that simulates high thermal endurance performance of a wet clutch system is modeled. This study applies CFD analysis to the lubricant convective flows that remove most of the frictional heat with respect to groove patterns on the frictional pad surface. Based on fluid flow analysis between the friction pad gap and the steel separator that includes the effects of pattern shapes on the friction pad, frictional heat, convective cooling behaviors and temperature distributions are computed with the repeated modes of varying sliding velocities and applied loads. The cooled frictional heat is investigated considering the convective flows in the gap of friction pad and separator. Frictional temperature variations on a wet clutch surface are computed for the effects of groove pattern shapes on the friction pad, waffle, and radial-arc types for better cooling effects. It is expected that the computational results will provide design methods for higher heat resistance durability and stable frictional torque transfer and effective cooling performance in wet clutch systems.

A study of Rate of Temperature Change during Tire Curing Using Computational Fluid Dynamics

The most important procedure in tire manufacturing is curing. The purpose of the curing is to apply high pressure and temperature over a period of time to unvulcanised rubber so that the rubber is cured to the point of best material properties. In this research, fluid flow analysis was considered to understand airflow pattern in an autoclave for a better quality of the product. We present preliminary results of the temperature distribution of heat transfer in an autoclave using Computational Fluid Dynamics package, OpenFOAM. The turbulent model was verified by comparison with the experimental results to obtain an accurate heat transfer coefficient. It was found that the error was 12%. The results from the simulation and experiments are in good agreement. Consequently, this turbulent model can be used to determine the heat transfer coefficient to achieve a better and more efficient curing process.

Minimization of entropy generation due to MHD double diffusive mixed convection in a lid driven trapezoidal cavity with various aspect ratios

Entropy generation minimization has significant importance in fluid flow, heat and mass transfer in an enclosure to get the maximum efficiency of a system and to reduce the loss of energy. In the present study, the analysis of mixed convection fluid flow, heat and mass transfer with heat line and mass line concept and entropy generation due to the effects of fluid flow, heat flow, mass flow and magnetic field in a trapezoidal enclosure with linearly heated and diffusive left wall, uniformly heated and diffusive lower wall, cold and nondiffusive right wall, adiabatic and zero diffusion gradient top wall have been reported. Parametric studies for the wide range of Prandtl number (Pr = 0.7 for air cooling system and Pr = 1000 for the engines filled with olive or engine oils), Rayleigh number (Ra = 103–105), aspect ratio (A = 0.5–1.5) and inclination angle of the cavity (ϕ = 45°–90°) have been performed, which help to construct the perfect shape of cavity in many engineering and physical applications so that the entropy is minimum to get the maximum efficiency of any system. The finite-difference approximation has been used to find out the numerical solutions. Biconjugate Gradient Stabilized (BiCGStab) method is used to solve the discretized nonhomogeneous system of linear equations.

Experimental Analysis of Semi-Open Impeller Pump as Turbine

Pump as turbine is one of the options for low-cost and simple electric power generation that suitable for rural area. Pump as turbine facing the same problem as any other hydropower plant which is low efficiency. Researchers focus on modification of the impeller, such as rounding, trimming, and surface smoothing. Most of the modified impeller was closed impeller type. The objective of this research was to investigate the possibility to generate more electric power of a PAT by using semi-open impeller. Simulation analysis was performed to analyze fluid flow in the pump housing. The simulation result shows the fluid velocity for open, semi-open and closed impeller is 646.87, 641.76, 639.89 m/s, respectively. The pressure of each open, semi-open and closed impeller is approximately 356, 361, and 388 kPa, respectively. The conclusion is that the open impeller had a higher velocity and lower pressure among two others. In the experimental testing, a semi-open impeller was selected because it had more strength and rigid body when it encountered the water impact. Three semi-open impellers with a blade thickness of 2, 4 and 6 mm made of brass were manufactured and tested. A close impeller which is the original impeller of the pump was also tested as a comparison. It is found that the open impeller with 2 mm blade thickness generated more electric power, approximately 36% than the original impeller.

Influence of frequency‐dependent anisotropy on seismic amplitude‐versus‐offset signatures for fractured poroelastic rocks

ABSTRACTFrequency‐dependent amplitude variation with offset offers an effective method for hydrocarbon detections and analysis of fluid flow during production of oil and natural gas within a fractured reservoir. An appropriate representation for the frequency dependency of seismic amplitude variation with offset signatures should incorporate influences of dispersive and attenuating properties of a reservoir and the layered structure for either isotropic or anisotropic dispersion analysis. In this study, we use an equivalent medium permeated with aligned fractures that simulates frequency‐dependent anisotropy, which is sensitive to the filled fluid of fractures. The model, where pores and fractures are filled with two different fluids, considers velocity dispersion and attenuation due to mesoscopic wave‐induced fluid flow. We have introduced an improved scheme seamlessly linking rock physics modelling and calculations for frequency‐dependent reflection coefficients based on the propagator matrix technique. The modelling scheme is performed in the frequency‐slowness domain and can properly incorporate effects of both bedded structure of the reservoir and velocity dispersion quantified with frequency‐dependent stiffness. Therefore, for a dispersive and attenuated layered model, seismic signatures represent a combined contribution of impedance contrast, layer thickness, anisotropic dispersion of the fractured media and tuning and interference of thin layers, which has been avoided by current conventional methods. Frequency‐dependent amplitude variation with offset responses was studied via considering the influences of fracture fills, layer thicknesses and fracture weaknesses for three classes amplitude variation with offset reservoirs. Modelling results show the applicability of the introduced procedure for interpretations of frequency‐dependent seismic anomalies associated with both layered structure and velocity dispersion of an equivalent anisotropic medium. The implications indicate that anisotropic velocity dispersion should be incorporated accurately to obtain enhanced amplitude variation with offset interpretations. The presented frequency‐dependent amplitude variation with offset modelling procedure offers a useful tool for fracture fluid detections in an anisotropic dispersive reservoir with layered structures.

Thermal Analysis of a Hydromagnetic Viscoelastic Fluid Flow Over a Continuous Curved Stretching Surface in the Presence of Radiative Heat Flux

This study deals with the flow and heat transfer of 2-D Maxwell fluid due to linear stretching of a curved surface. The heat transfer happens when temperature is specified on the boundary as prescribed surface temperature, PST, and prescribed surface heat flux, PSHF. The radiation and dissipation effects are incorporated in the energy equation. The modeling of the curved structure for a linear stretching velocity of Maxwell fluid is developed. The fluid is electrically conducted in the presence of varying applied magnetic field. The field quantities which describe the velocity, pressure, and temperature are calculated numerically. The effects of the radius of curvature, magnetic field, and non-Newtonian parameters are investigated and explained physically. This analysis adds to the mathematical understanding of boundary-driven flows in non-Newtonian fluids and enlarges the scope of its applications in the polymer industry for curved structures.

Supercritical CO2 conjugate heat transfer and flow analysis in a rectangular microchannel subject to uniformly heated substrate wall

In this paper, a conjugate heat transfer and fluid flow analysis for supercritical CO2 (sCO2) was numerically investigated in a rectangular microchannel subject to uniform heat flux on the bottom of the substrate wall. The study was conducted to explore and quantify the effect of a sharp variation of sCO2 transport properties, Reynolds number and operational pressure conditions on the fluid flow and heat transfer in the pseudo-critical region and within close range of the Critical Point (CP). The numerical results indicate that the large variation of sCO2 properties within close range of the CP affects the heat transfer and flow along the channel. The local flow and heat transfer analyses demonstrate that the wall shear stress and heat flux are an increasing function of operating conditions especially for operational pressures higher than the critical pressure. The results show that the large variation of Nusselt number disappears for high operating pressures. It was also shown that the Nusselt Number is not affected by the Reynolds number in the laminar regime at high operating pressures.

Computational Analysis for Unsteady and Steady Magnetohydrodynamic Radiating Nano Fluid Flow past a Slippery Stretching Sheet Immersed in a Permeable Medium

This work gives an account of unsteady and steady radiating magnetohydrodynamics (MHD) nanofluid flow over a slippery stretching sheet embedded in a porous medium. A widely used similarity variables of such flows reduces a governing partial differential equations (PDEs) into a new set of partial differential equations (PDEs) in which a dependent variable is a function of two independent variables rather than three. At the same time, third order PDEs are converted into a second order PDEs by defining a new variable wherever it is deemed necessary. For the time integration, we perform first order explicit Euler method and spatial derivatives are approximated by the finite difference formulas in the context of node-centered finite volume method. It is revealed that for the unsteady flow the temperature of the nanofluid is higher near the surface without thermophoresis parameter Nt and reduced significantly when Nt is present. We also show that the concentration boundary layer thickness decreases with an increase of Darcy number Da.

Analysis of Fluid Flow of Liquid Steel through Clogged Nozzles: Thermodynamic Analysis and Flow Simulations

Selected raw materials, surface treatment, and control of the internal flow fundamentals are applied to manufacture an anticlogging nozzle. This nozzle is compared with another one manufactured with a conventional alumina–graphite (AG) composite in a plant trial. The two nozzles, with and without clogging, are replicated with plastic and rubber materials and the flows, under unclogged and clogged conditions, are characterized using water modelling and mathematical simulations. The new nozzle material yields considerably less clogging than the nozzle with the conventional AG after casting four heats, yet, there is still clogging. Flow patterns, because of clogging, change radically and represent serious conditions for slab integrity and the productivity of the caster.

Thermal analysis of magnetized pseudoplastic nano fluid flow over 3D radiating non-linear surface with passive mass flux control and chemically responsive species

The process of fluid flow over three-dimensional (3D) domains has valuable and promising applications in multiple disciplines like in aerodynamics, computer graphics, environmental science, material synthesis technology, geographic information system, polymer industry and so forth. So, in view of such admirable utilization of fluid flowing processes over 3D surfaces current effort is presented to examine the flow behavior of non-Newtonian fluid past a bidirectional non-linearly stretched sheet. In this regards, Williamson model is considered which represent speculative features of shear thinning materials which are obliged in biomechanics, lubricants formation, polymer solution, suspension etc. Momentum transport with in flow field is envisioned by the appliance of transversally directed magnetic. The novelty of analysis is strengthened by Fourier heat flux and Buongiorno mass conservation models. Mathematical modelling of conventional energy equation is modified by incorporation of nanofluid Brownian and thermophoresis effects. The condition of zero normal flux of nanoparticles at the stretching surface is defined to impulse the particles away from the surface in combination with nonzero normal flux condition. Mathematical modelling of Williamson fluid including the impact of chemical reaction, radiative heat flux and heat source is manifested in the form of partial differential equations. Similarity variables are capitalized to transmute governing modelled conservation laws in to ordinary non-dimensionalzed expressions. Assessment of flow attributing profiles is disclosed by implementing Runge-Kutta-Fehlberg procedure (RKF-45) in collaboration with shooting method. Behavior of momentum, temperature and concentration distributions against miscellaneous arising parameters is visualized through graphical structures. Graphical visualization and numerical data about surface drag coefficients and heat and mass transfer rates are also presented. The computed solution is in excellent agreement with existing data in a limiting sense which assures the credulity of this work.

Stability Analysis of MHD Fluid Flow over a Moving Plate with Pressure Gradient Using the Chebyshev Spectral Method

The purpose of this paper is to investigate the magnetohydrodynamic stability external flow of a viscous, incompressible and electrically conducting fluid over a moving flat plate using temporal linear stability analysis. Using a similarity variables based on the Skan-Falkner transformation, the governing differential equations of mean flow are transformed into a nonlinear ordinary differential equation, which is then solved numerically by the Runge-Kutta method. The MHD stability equation is solved numerically by using the Chebyshev spectral collocation method, which is based on the eigenfunction expansion in terms of Chebyshev polynomials, collocation points, and the subsequent solution of the resulting generalized eigenvalue problem with the QZ algorithm. The influence of the pressure gradient, magnetic field and wall velocity on the dimensionless mean velocity are presented graphically and discussed. For the disturbance flow in the presence of magnetic field and moving wall, the critical Reynolds number increases with increasing the magnetic field parameter and wall velocity, indicating that these parameters stabilize the flow.