Turbulent Flow In Circular Pipe Research Articles

Comparison of Mean Properties of Turbulent Pipe and Channel Flows at Low-to-Moderate Reynolds Numbers

We focus on the fully developed turbulent flow in circular pipes and channels. We provide a comparison of the mean velocity profiles, and we compute the values of the global indicators, such as the skin friction, the mean velocity, the centerline velocity, the displacement thickness, and the momentum thickness. The comparison is done at low-to-moderate Reynolds numbers. For channel flow, we deduced the mean velocity profiles using an indirect turbulent model; for pipe flow, we extracted the needed information from a direct numerical simulation database available in the open literature. A one-to-one comparison of these values at identical Reynolds numbers provides a deep insight into the difference between pipe and channel flows. This line of reasoning allows us to highlight some deviations among the mean velocity profiles extracted from different pipe databases.

Experimental investigation of the heat transfer and friction loss of turbulent flow in circular pipe under low-frequency ultrasound propagation along the mainstream flow

The characteristics of the heat transfer and friction loss of turbulent water flow in a circular pipe were investigated experimentally at a constant surface temperature of 45 ℃ for 28 kHz ultrasound propagation along the mainstream flow. Transducers were installed in five rows and three columns in the upstream section of the test pipe, and the number of active transducers was varied (1, 3, and 15) for a Reynolds number range of 10,000–25,000. The results indicated that the ultrasonic effects yielded positive results for both the heat transfer and pressure loss of the pipe flow. Under the influence of 15 ultrasonic transducers, the maximum Nusselt number ratio was 1.57 and the greatest reduction in the friction factor was 21.6 % for a Reynolds number of 10,000. The corresponding maximum thermal performance factor was approximately 1.7. However, the thermal efficiency tended to decrease with an increase in the number of transducers. The maximum thermal efficiency values under ultrasonic waves with 1, 3, and 15 transducers were 5.43, 3.37, and 1.95, respectively. When the change in the friction factor per ultrasonic input power was considered, the most suitable number of ultrasonic transducers was three. Finally, predictive formulas were proposed for the Nusselt number ratio and friction factor ratio under low-frequency ultrasound, with deviations from −5.5 % to 5.4 % and −7.4 % to 7.4 %, respectively.

Secondary Flow in Smooth and Rough Turbulent Circular Pipes: Turbulence Kinetic Energy Budgets

Direct Numerical Simulations have been performed for turbulent flow in circular pipes with smooth and corrugated walls. The numerical method, based on second-order finite discretization together with the immersed boundary technique, was validated and applied to various types of flows. The analysis is focused on the turbulence kinetic energy and its budget. Large differences have been found in the near-wall region at low Reynolds number. The change in the near-wall turbulent structures is responsible for increase of drag and turbulence kinetic energy. To investigatselinae the effects of wall corrugations, the velocity fields have been decomposed so as to isolate coherent and incoherent motions. For corrugated walls, we find that coherent motions are strongest for walls covered with square bars aligned with the flow direction. In particular, the coherent contribution is substantial when the bars are spaced apart by a distance larger than their height. Detailed analysis of the turbulence kinetic energy budget shows for this set-up a very different behavior than for the other types of corrugations.

Heat Transfer and Fluid Flow Analysisfor Turbulent Flow in Circular Pipe with Vortex Generator

The performance of heat transfer enhancement (HTE) using modified inserts (MIs) as a vortex generator in pipe flow and fluid flow analysis using computational fluid dynamics (CFD) are evaluated in this article. The MIs are fastened to the central rod, and the circular sections of the MIs touched the circular wall of the test pipe. Heat transfer and fluid flow analyses are carried out for the various pitch to diameter ratios (P/D) and angles of the MIs. P/D ratios of 3, 4 and 6 and MIs angles of 15°, 30°, 45°, 60° and 90° are considered for experimental analysis. CFD analysis is carried out for P/D ratios of 3, 4 and 6 and MIs angles of 30°, 45° and 90°. Nusselt number (Nu/Nus) and friction factor (f/fs) ratios are evaluated using the same Reynolds number between 8000 and 17,000 in the experimental study. The MIs encourage the wall and core fluid to be combined thus helps in HTE. It is found that, as the P/D ratio increases, the Nu/Nus and f/fs decrease. If the distance between the MIs increases, the mixing of fluid weakens. With decreasing the P/D ratio, Nu/Nus increases. Increased fluid mixing leads to a higher coefficient of heat transfer and higher values of pressure drop. A P/D ratio of 4 and MIs angle of 45° results in greater heat interaction than others. Finally, recommendations for the best P/D ratio and angles of MIs are made for improved HTE on fluid flow through a circular pipe.Article HighlightsModified inserts (MIs) are used inside the test pipe to check the heat transfer enhancement at various angles. Also, compared the performance with and without MIs.Fluid flow analysis is checked by CFD (Fluent) in Ansys software.Fluid flow patterns for various MIs angles and P/D ratios are compared.

Experimental investigation on heat transfer in laminar, transitional and turbulent circular pipe flow with respect to flow regime boundaries

The empirical prediction methods for heat transfer coefficients in the transition regime between laminar and fully turbulent flow are still subject to changes. This situation reflects a lack of reliable experimental data, which are consistently determined over a wide range of relevant Reynolds and Prandtl numbers. This contribution presents new measurement data, in particular 164 data points for heat transfer coefficients, consistently determined over a wide range of Reynolds and Prandtl numbers, ranging from 13 < Pr < 70 and 375 < Re < 13100. In addition, the widely accepted prediction method for heat transfer in circular pipes according to Gnielinski is tested with the present data and other relevant data from literature. This method relies on a linear interpolation between the heat transfer coefficients at the onset of the transition regime and that of the fully turbulent regime. Consequently, working on a consensus about the values of these onset points is an important issue. In this contribution, the transitional flow regime has been found to start at Recr = 2300, and the fully turbulent flow regime to start in the range of 4100 < Ret < 5400. Those findings support the latest version of Gnielinski’s method, published in 2013, as well as other recent work on the topic, particularly that of Everts and Meyer.

Effect of Reynolds Number and Concentration of Biopolymer (Gum Arabic) on Drag Reduction of Turbulent Flow in Circular Pipe

Effect of Reynolds Number and Concentration of Biopolymer (Gum Arabic) on Drag Reduction of Turbulent Flow in Circular Pipe

Experimental investigation on heat transfer in laminar, transitional and turbulent circular pipe flow

Experimental investigations on heat transfer in a circular pipe for laminar, transitional and turbulent flow are presented. Reliable prediction of heat transfer coefficients for transitional flows is still a challenging task. While methods for predicting laminar and turbulent heat transfer coefficients are widely established in literature, the proposed methods and the validity for calculating according values for the transition region and even the definition of this region itself remains a field of ongoing development. One aspect in this picture is the scarce availability of experimental data on heat transfer coefficients in circular pipe flow for Reynolds numbers in the range of 1000<Re<4000, especially for higher Prandtl numbers, i.e. 10<Pr<90. Thus, this paper focuses on providing experimental results for heat transfer in circular pipe flow for Reynolds (Re) numbers in the range of 500<Re<23000 and 7<Pr<41. The test fluid is a water–glycol mixture with a mass fraction of water of xm=0.477. The results presented in this paper show good agreement with the widely used calculation methods proposed by Gnielinski in 2013 for laminar, transitional and turbulent flow. The results also confirm the presence of the transition region to occur between 2300<Re<4000. 184 data points in the range of 1000<Re<4000 are shown, since in this range scarce data are available in literature. In summary 261 heat transfer coefficients for 500<Re<23000 and 7<Pr<41 are presented, which show good agreement (80.8% are within ±15%) to the cited literature.

Discrete Tracer Point Method to Evaluate Turbulent Diffusion in Circular Pipe Flow

Diffusion of a solute in turbulent flows through a circular pipe or tunnel is an important aspect of environmental safety. In this study, the diffusion coefficient of turbulent flow in circular pipe has been simulated by the Discrete Tracer Point Method (DTPM). The DTPM is a Lagrangian numerical method by a number of imaginary point displacement which satisfy turbulent mixing by velocity fluctuations, Reynolds stress, average velocity profile and a turbulent stochastic model. Numerical simulation results of points’ distribution by DTPM have been compared with the analytical solution for turbulent plug-flow. For the case of turbulent circular pipe flow, the appropriate DTPM calculation time step has been investigated using a constantβ, which represents the ratio between average mixing lengths over diameter of circular pipe. The evaluated values of diffusion coefficient by DTPM have been found to be in good agreement with Taylor’s analytical equation for turbulent circular pipe flow by givingβ=0.04 to 0.045. Further, history matching of experimental tracer gas measurement through turbulent smooth-straight pipe flow has been presented and the results showed good agreement.

The effect of lattice models within the lattice Boltzmann method in the simulation of wall-bounded turbulent flows

This study investigated the effect of 3D lattice models (D3Q19 and D3Q27 lattices) on the simulation results of wall-bounded turbulent flows in a circular pipe and in a square duct. The LES with the Smagorinsky subgrid-scale (SGS) model was adopted for the turbulence simulation. To improve the credibility of our results on the lattice model effect, a comprehensive sensitivity study was performed of boundary treatment techniques and collision models, as well as grid sizes in the simulation of the turbulent pipe flows. Through the turbulent circular pipe flow simulation, it was discovered that the D3Q27 lattice model could achieve the rotational invariance in terms of long-time-averaged turbulence statistics and generated the results comparable to the DNS data, while the D3Q19 lattice model broke the rotational invariance and produced unreasonable data. In the turbulent square duct flow simulation, the rotational invariance was evaluated by comparing the results before and after rotating the geometry by 45° about a center. As in the circular pipe flow simulation, the D3Q19 lattice model could not achieve the rotational invariance while the D3Q27 lattice model could. The D3Q19 lattice model also produced poor results compared to those from the D3Q27 lattice model. These defects of the D3Q19 lattice model could be explained by the planes consisting of 2D lattices with five velocities (called defective planes in this study) in the D3Q19 lattice model, based on White and Chong’s [14] hypothesis. The defective planes had a deficiency in the momentum transfer of flow and turbulence, thus breaking the rotational invariance and causing the inaccurate results for tested problems.

Enhancing heat transfer in vortex generator-type multifunctional heat exchangers

Global and local analysis of the heat transfer in turbulent vortical flows is studied using three-dimensional numerical simulations. Vorticity is generated by inclined vortex generators in a turbulent circular pipe flow with twelve different configurations that fall into three categories. In the first category are rows of trapezoidal vortex generators in different arrangements; in the second category the vortex generators are fixed at certain distance from the tube wall, and the third category has vortex generator rows between which a row of small protrusions are inserted on the tube wall. First, a global analysis of the thermal performance is performed for all these configurations, which are also compared with other heat exchangers from the literature. New correlations for the friction factor and Nusselt number are then obtained. Local analysis of the effect of the flow structure on the temperature distribution is carried out for the four configurations showing the best performances. The local analysis involves studying the streamwise vorticity flux to characterize the convective transport process, the turbulent kinetic energy characterizing the turbulent mixing, and finally the local Nusselt number.

Estimation of Time-Varying Inlet Temperature and Heat Flux in Turbulent Circular Pipe Flow

Abstract This study addresses the conjugate heat transfer problem of hydrodynamically developed turbulent flow in a circular pipe. An inverse method is used to estimate the time-varying inlet temperature and the outer-wall heat flux simultaneously on the basis of temperature measurements taken at two different locations within the pipe flow. The present approach rearranges the matrix forms of the governing differential equations and then applies a whole domain estimation with the function specification method and the linear least-squares-error method to determine the two boundary conditions of the pipe flow. The dimensionless temperature data obtained from the direct problem are used to simulate the temperature measurements. The influence of temperature measurement errors upon the precision of the estimated results is investigated. The proposed method provides several advantages compared to traditional methods: (1) it yields a solution within a single computational iteration, (2) no prior information is required regarding the functional form of the quantities of interest, (3) no initial guesses of the unknown parameter values are required, and (4) the inverse problem can be solved in a linear domain. This study also considers the influence of the location of the temperature measurement sensors upon the accuracy of the calculated results. The numerical results confirm that the proposed method provides an efficient, robust, and accurate means of estimating the inlet temperature and outer-wall heat flux simultaneously in turbulent pipe flow.

Estimation of unknown outer-wall heat flux in turbulent circular pipe flow with conduction in the pipe wall

This study addresses the conjugate heat transfer problem of thermally developing, hydrodynamically developed turbulent flow in a circular pipe. An inverse method is used to estimate the unknown heat flux on the external surface of the circular pipe based on temperature measurements taken at several different locations within the fluid. The present approach rearranges the matrix forms of the governing differential equations, and then applies the linear least-squares-error method to determine the unknown boundary conditions of the pipe flow. The results confirm that the proposed method is capable of yielding accurate results even when errors in the temperature measurements are present, and that the accuracy of the estimated results is improved by taking temperature measurements in locations close to the inner-wall.

G401 円管流の層流乱流遷移の色素流入実験による検証

G401 円管流の層流乱流遷移の色素流入実験による検証

A first course in fluid mechanics for civil engineers

Book review / Critiques de livres Dr. Gray is presently an Associate Professo in the Department of Civil and Environmental Engineering at West Virginia University at Morgantown in West Virginia. He has considerable experience in teaching fluid mechanics, has published over 100 papers and reports in fluid mechanics, and also has industrial experience. He wrote this text in fluid mechanics for a one-semester course for civil, environmental, and agricultural engineers to provide a narrower focus rather than attempt to cover the whole range of fluid mechanics. Dr. Gray believes that such a narrow focus might motivate the students more readily. This book uses both the US Customary and SI systems of units. This book has 15 chapters and two appendices that deal with Tables of Fluid Properties and Answers to Selected Problems; it also has a Subject Index. The first chapter presents the scope of engineering fluid mechanics — a brief description of many books dealing with fluid mechanics along with a discussion of units. The second chapter treats fluid properties with the discussion of viscosity left to a later chapter. Chapters 3 and 4 present a thorough discussion of the principles of hydrostatics, covering pressure distribution in liquids, manometers, idea of piezometric head, stratified layers, and force exerted on plane surfaces. Discussion of force exerted on curved surfaces and buoyancy is delayed until chapter 14. Chapter 5 presents a discussion of fluid dynamics, starting with the development of the Euler equation along the streamline and its integration to obtain the Bernoulli equation. The author then uses the Bernoulli equation to present and discuss a number of elementary problems like water jets in air, pitot and pitot-static tubes, venturimeter, and sharpcrested weirs. Chapter 5 closes with the development of the Euler equations in the Cartesian system with the Z axis in the vertical direction. Chapter 6 is a rather lengthy presentation of the mass conservation equation. Chapter 7 presents a discussion of viscosity and a detailed derivation of fully developed laminar flor in a circular pipe and ends with a partially complete derivation of the NavierStokes equation in the Cartesian system. Chapter 8 presents a good derivation of the energy equation, which is correctly identified as different from the Bernoulli equation. The idea of the piezometric and total heads is discussed along with some standard problems. Chapter 9 is entitled Pipe Flow 1 and develops the Poiseuille equation using the energy equation and the results derived from chapter 7. It also presents a short discussion of turbulent flow. Chapter 10 presents a brief discussion on dimensional analysis. Pipe Flow 2 constitutes chapter 11, which deals with head loss for turbulent flow in circular pipes, discusses the Moody Diagram, minor losses, and standard pipe flow problems with some comments on turbulent flow in non-circular pipes. The momentum equation is developed in Chapter 12 along with a thorough discussion of a number of problems. Chapter 13 deals with open channel flow. It discusses uniform flow using the Manning equation as well as the friction factor method and nonuniform flow using the idea of the specific head. It also deals with gravity waves including the hydraulic jump. Chapter 15 deals with physical models and similarity. It discusses geometrically similar Reynolds and Froude models as well as some distorted models and ends with brief comments on river models. The treatment of the Euler and Navier-Stokes equations in the Cartesian system could have been made more general by tilting the axes and combining the pressure and body force terms into piezometric gradients. This set of Euler equations could have been integrated to obtain the Bernoulli equation, which would have required the author to present at least a brief treatment of vorticity and potential flow. Further, using the Navier-Stokes equations, the author could have shown how these equations could be simplified to solve a few simple flows, including the Poiseuille equation, in an elegant manner. On the whole, this book is written clearly; it emphasizes engineering relevance, presents numerous worked-out examples, and provides a number of problems for the reader to solve. I think that this book provides a pragmatic introduction to engineering fluid mechanics for students in civil engineering, including environmental and agricultural engineering, and I would recommend this book to them.

A first course in fluid mechanics for civil engineers

Book review / Critiques de livres Dr. Gray is presently an Associate Professo in the Department of Civil and Environmental Engineering at West Virginia University at Morgantown in West Virginia. He has considerable experience in teaching fluid mechanics, has published over 100 papers and reports in fluid mechanics, and also has industrial experience. He wrote this text in fluid mechanics for a one-semester course for civil, environmental, and agricultural engineers to provide a narrower focus rather than attempt to cover the whole range of fluid mechanics. Dr. Gray believes that such a narrow focus might motivate the students more readily. This book uses both the US Customary and SI systems of units. This book has 15 chapters and two appendices that deal with Tables of Fluid Properties and Answers to Selected Problems; it also has a Subject Index. The first chapter presents the scope of engineering fluid mechanics — a brief description of many books dealing with fluid mechanics along with a discussion of units. The second chapter treats fluid properties with the discussion of viscosity left to a later chapter. Chapters 3 and 4 present a thorough discussion of the principles of hydrostatics, covering pressure distribution in liquids, manometers, idea of piezometric head, stratified layers, and force exerted on plane surfaces. Discussion of force exerted on curved surfaces and buoyancy is delayed until chapter 14. Chapter 5 presents a discussion of fluid dynamics, starting with the development of the Euler equation along the streamline and its integration to obtain the Bernoulli equation. The author then uses the Bernoulli equation to present and discuss a number of elementary problems like water jets in air, pitot and pitot-static tubes, venturimeter, and sharpcrested weirs. Chapter 5 closes with the development of the Euler equations in the Cartesian system with the Z axis in the vertical direction. Chapter 6 is a rather lengthy presentation of the mass conservation equation. Chapter 7 presents a discussion of viscosity and a detailed derivation of fully developed laminar flor in a circular pipe and ends with a partially complete derivation of the NavierStokes equation in the Cartesian system. Chapter 8 presents a good derivation of the energy equation, which is correctly identified as different from the Bernoulli equation. The idea of the piezometric and total heads is discussed along with some standard problems. Chapter 9 is entitled Pipe Flow 1 and develops the Poiseuille equation using the energy equation and the results derived from chapter 7. It also presents a short discussion of turbulent flow. Chapter 10 presents a brief discussion on dimensional analysis. Pipe Flow 2 constitutes chapter 11, which deals with head loss for turbulent flow in circular pipes, discusses the Moody Diagram, minor losses, and standard pipe flow problems with some comments on turbulent flow in non-circular pipes. The momentum equation is developed in Chapter 12 along with a thorough discussion of a number of problems. Chapter 13 deals with open channel flow. It discusses uniform flow using the Manning equation as well as the friction factor method and nonuniform flow using the idea of the specific head. It also deals with gravity waves including the hydraulic jump. Chapter 15 deals with physical models and similarity. It discusses geometrically similar Reynolds and Froude models as well as some distorted models and ends with brief comments on river models. The treatment of the Euler and Navier-Stokes equations in the Cartesian system could have been made more general by tilting the axes and combining the pressure and body force terms into piezometric gradients. This set of Euler equations could have been integrated to obtain the Bernoulli equation, which would have required the author to present at least a brief treatment of vorticity and potential flow. Further, using the Navier-Stokes equations, the author could have shown how these equations could be simplified to solve a few simple flows, including the Poiseuille equation, in an elegant manner. On the whole, this book is written clearly; it emphasizes engineering relevance, presents numerous worked-out examples, and provides a number of problems for the reader to solve. I think that this book provides a pragmatic introduction to engineering fluid mechanics for students in civil engineering, including environmental and agricultural engineering, and I would recommend this book to them.

Effect of entrance conditions on the development of turbulent flow in circular pipes

New experimental data is presented on the stabilization length of the velocity profile in circular pipes as a function of entrance conditions. The experimental channel used was a machined pipe 145 mm in diameter consisting of 23 sections each 600 mm long. The sections were machined to second-class accuracy with an inner surface roughness of 0.32. The individual sections were connected and centered by sleeves. Packing grease was applied to the outer surface of the pipe against the fittings. The experiments were performed with a confined stream of air at a Reynolds number of 285,000. The velocity profiles and turbulence intensity were measured by the hot-wire anemometer method. The apparatus included a bridge with a constant temperature filament, an amplifier, a linearizer, and an RMS voltmeter.

Flow of Liquid Metals with a Transversely Applied Magnetic Field : 5th Report, Skin Friction Coefficient of Turbulent Circular Pipe Flow

Flow of Liquid Metals with a Transversely Applied Magnetic Field : 5th Report, Skin Friction Coefficient of Turbulent Circular Pipe Flow

On the use of the Preston tube in elliptical ducts

The principle of wall similarity expressed by a universal logarithmic inner law relationship is well established for turbulent flow in circular pipes. The validity of Preston's original hypothesis for the measurement of turbulent skin friction depends upon the existence of wall similarity. Although Preston's hypothesis appears to be correct in general it has been found that his calibration for the wall pitot tube was incorrect. Extensive observations by Head and Rechenberg showed some discrepancy. Later work by Patel on the measurement of skin friction in three circular pipes covering a much larger experimental range has led to a modified calibration.

Momentum, Heat, and Mass Transfer Analogy for Turbulent Flow in Circular Pipes

Momentum, Heat, and Mass Transfer Analogy for Turbulent Flow in Circular Pipes

Momentum, Heat, and Mass Transfer Analogy for Turbulent Flow in Circular Pipes

Momentum, Heat, and Mass Transfer Analogy for Turbulent Flow in Circular Pipes