Estimation Of Friction Factor Research Articles

Estimation of friction factor and bed shear stress considering bedform effect in rivers

AbstractThe roughness height plays a crucial role, especially in shallow‐water environments with rough‐bed conditions. Specifically, it is a key parameter for predicting flow velocity and bed shear stress. Therefore, an accurate determination of roughness height is essential for precise predictions of hydraulic phenomena. In this study, we propose a method to estimate form roughness height and friction factor using bathymetry data, with a focus on cross‐sectional data in the transverse direction. To overcome the limitations of using lateral direction data, we derived an empirical formula for estimating bedform length from the bed profiles in the streamwise direction. To assess the validity of bedform analysis and estimated form roughness height based on lateral direction data, we compared the characteristics of bedform and form roughness height analysed using lateral direction data with those analysed using the streamwise direction data. Furthermore, we confirmed the importance of considering the form roughness height in estimating bed shear stress through a comparison with bed shear stress calculations considering only grain roughness height.

Estimation of Bedform Friction Factor Directly from Bathymetry Data

We present a procedure to systematically estimate the form friction factor through the analysis of spatial data obtained by acoustic Doppler current profiler. The form friction factor is related to the geometric characteristics of the bedform. The zero-crossing method was used to determine the geometric parameters of the bedform, which were then utilized to construct the probability density function for Chezy coefficients. Subsequently, Chezy coefficients were generated from the probability density function and assigned to each grid cell of a numerical model. To evaluate the performance of the presented friction factor estimation method, it was applied to the numerical simulation for the Nakdong River in South Korea. Sensitivity tests were performed to address the potential influence of random extraction from the probability density function, filtering length, and different form predictors during the estimation process. The proposed method showed more robust and accurate results compared to those with Manning's n value.

Estimation of heat transfer coefficient and friction factor with showering of aluminum nitride and alumina water based hybrid nanofluid in a tube with twisted tape insert

Twisted tape is one of the active thermal proficiency boosting technology which has been deeply examined because to consistent efficiency findings and easy implementations. Thermo-hydraulic effectiveness of tubes fitted with twisted tapes is becoming highly significant. Although twisted tapes can cause swirls and disturb boundary layers, this is the most widely used method for improving convection. In the present attempt, to enhance the heat transfer twisted tape is inserted in tube. In the current modern research, the effect of twisted tape, on the enhancement of thermal transport, Nusselt number and friction factor performance of AIN–Al2O3/water hybrid nanofluid is evaluating utilizing CFD and ANSYS-FLUENT software. the consequence of twisted pitch 44 mm, 66 mm, 88 mm, 100 mm and Reynolds numbers 800, 1200, 1600 and 2000 on Nusselt number, heat transfer coefficient and friction coefficient have been computed numerically with 0.01 to 0.04 volume friction of nanopowders. The commercial ANSYS-FLUENT code was used in this analysis utilizing the SIMPLE method for pressure–velocity coupling. The K-ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$K - \\omega$$\\end{document} model and Navier Stokes equations are integrating utilizing finite volume method in ANSYS-FLUENT. It was observed that inserting the twisted tape in tube significantly improves the thermal conductivity as well as friction factor compared with the simple tube without turbulator.

Experimental and numerical study of an innovative twined tube HX design

An innovative twined tube heat exchanger (HX) design is proposed, which is simple, robust, and efficient for use in advanced nuclear reactors. The heat exchanger is designed with two tubes twined around each other. Multiple modules can be assembled within a shell to meet the necessary heat load. Thermal-hydraulic investigations of the novel design are performed through experiments and numerical simulation. The experimental investigations of the twined tube HX are carried out on a laboratory-scale thermal–hydraulic rig commissioned at the Pakistan Institute of Engineering & Applied Sciences (PIEAS). The primary loop contains water at a high temperature and a pressure of 4.0 bar pressure, while the secondary loop operates at atmospheric pressure. Single-phase forced convection heat transfer characteristics of the twined tube HX are investigated experimentally. Pressure drop is measured for mass fluxes ranging from 350 kg/m2s to 1376 kg/m2s. A correlation for the estimation of friction factor is developed based on the experimental studies. Heat transfer measurements are carried out for mass fluxes ranging from 244 kg/m2s to 419 kg/m2s. Based on these experiments, the Nusselt number is evaluated for the mass flux range mentioned above. The numerical simulations of a twined tube HX are performed on a full-scale STAR-CCM + model. The model is validated against the experimental results. The performance factor of the twined tube HX is higher than that of straight tube HX, with a maximum performance enhancement of 60%. The thermal–hydraulic performance of the twined tube HX is comparable with helical coil HX designs. However, the proposed HX design is easier to fabricate and maintain than the helical coiled HX. Overall, the study provides valuable insights into the thermal–hydraulic performance of the twined tube HX, which could be useful in the design of compact and efficient heat exchangers for small modular reactors.

Application of AI-Based Techniques on Moody’s Diagram for Predicting Friction Factor in Pipe Flow

The friction factor is a widely used parameter in characterizing flow resistance in pipes and open channels. Recently, the application of machine learning and artificial intelligence (AI) has found several applications in water resource engineering. With this in view, the application of artificial intelligence techniques on Moody’s diagram for predicting the friction factor in pipe flow for both transition and turbulent flow regions has been considered in the present study. Various AI methods, like Random Forest (RF), Random Tree (RT), Support Vector Machine (SVM), M5 tree (M5), M5Rules, and REPTree models, are applied to predict the friction factor. While performing the statistical analysis (root-mean-square error (RMSE), mean absolute error (MAE), squared correlation coefficient (R2), and Nash–Sutcliffe efficiency (NSE)), it was revealed that the predictions made by the Random Forest model were the most reliable when compared to other AI tools. The main objective of this study was to highlight the limitations of artificial intelligence (AI) techniques when attempting to effectively capture the characteristics and patterns of the friction curve in certain regions of turbulent flow. To further substantiate this behavior, the conventional algebraic equation was used as a benchmark to test how well the current AI tools work. The friction factor estimates using the algebraic equation were found to be even more accurate than the Random Forest model, within a relative error of ≤±1%, in those regions where the AI models failed to capture the nature and variation in the friction factor.

CFD-based Estimation of Friction Factor in Rough Pipes with Herschel-Bulkley Fluids

The appropriate estimation of frictional losses in a pipeline system is essential. So far, little attention has been paid to determining the friction factors with non-Newtonian fluids, especially in rough pipes. This study aims at calculating the friction factor using validated three-dimensional Computational Fluid Dynamics models in Ansys CFX. Steady-state computations are performed with three different incompressible Herschel-Bulkley fluids in rough pipes with relative roughness of the inner pipe surface ε = 0.0005 – 0.01. A power-law type bath gel as a test fluid is used for experiments to validate our numerical model. The numerical results are compared with the measured values and also with numerous existing friction factor estimation models with the help of generalization of the Reynolds number in the relevant engineering range of Regen = 100 – 40,000. This paper shows that the existing approximations can not accurately describe the friction factor with pseudoplastic fluids in rough pipes. On the contrary, in the case of Bingham plastic fluid, a new, explicit calculation relation is found in a unified form accepted by the literature.

Effect of Base Angle of an Isosceles Trapezoidal Solar Air Heater Duct on Flow and Thermal Characteristics—A Numerical Investigation

Abstract This paper reports the computational results of fluid flow and thermal characteristics in an isosceles trapezoidal solar air heater (SAH). By varying the base angle of the trapezoidal duct from 90 deg to 45 deg, six different models of solar air heater ducts are obtained. The six geometries of SAH ducts have cross sections of rectangular (90 deg), triangular (45 deg), and four isosceles trapezoidal (having base angles of 50 deg, 60 deg, 70 deg, and 80 deg) shapes. The solar radiation absorber plate width and the duct heights are maintained constant for all six models of SAH, i.e., 160 mm and 80 mm, respectively. The SAH is subjected to a constant and uniform heat flux value of 1000 W/m2 and Reynolds numbers varied from 5000 to 28,000. In all six cases, the size of the air heater is the same and having dimensions of 0.16 m width and 1 m length. For this investigation, a three-dimensional computational model has been developed and simulations are carried out using commercially available ansys fluent software. The numerical results are validated with the standard correlations and literature data, and a suitable model has been identified for the turbulence closure. A detailed analysis of the Nusselt number, temperature distribution over the SAH, and friction factor across the SAH duct is done. Empirical correlations for the estimation of heat transfer and friction factor have been developed as functions of the base angle of the duct and Reynolds number. An overall performance factor (λ) is adopted to get the combined effect of friction factor and Nusselt number with an intention to arrive at the optimum base angle of the SAH duct, and optimum geometry is identified. Based on the value of λ, it is concluded that the SAH duct with the highest base angle (90 deg) in this investigation, i.e., the rectangular duct, is the optimum among all the ducts considered in the study.

Investigation into the Computational Costs of Using Genetic Algorithm and Simulated Annealing for the Optimization of Explicit Friction Factor Models

Research reports show that the accuracies of many explicit friction factor models, having different levels of accuracies and complexities, have been improved using genetic algorithm (GA), a global optimization approach. However, the computational cost associated with the use of GA has yet to be discussed. In this study, the parameters of sixteen explicit models for the estimation of friction factor in the turbulent flow regime were optimized using two popular global search methods namely genetic algorithm (GA) and simulated annealing (SA). Based on 1000 interval values of Reynolds number (Re) in the range of and 100 interval values of relative roughness () in the range of , corresponding friction factor (f) data were obtained by solving Colebrook-White equation using Microsoft Excel spreadsheet. These data were then used to modify the parameters of the selected explicit models. Although both GA and SA led to either moderate or significant improvements in the accuracies of the existing friction factor models, SA outperforms the GA. Moreover, the SA requires far less computational time than the GA to complete the corresponding optimization process. It can therefore be concluded that SA is a better global optimizer than GA in the process of finding an improved explicit friction factor model as an alternative to the implicit Colebrook-White equation in the turbulent flow regime.

Design, imaging and performance of 3D printed open‐cell architectures for porous electrodes: quantification of surface area and permeability

AbstractBACKGROUNDThe development of new open‐cell porous electrodes for electrochemical flow cells and reactors is demonstrated through the application of 3D printing. The properties of diverse architectures were investigated, including rectangular, circular, hexagonal and triangular cells with linear porosity grades of 10, 20 and 30 pores per inch (ppi). Specimens were digitally designed, then 3D printed in stainless steel via selective laser melting. After being examined using scanning electron microscopy, they were characterized in terms of volumetric surface area and porosity with the aid of X‐ray computed tomography. Pressure drop measurements were performed over a range of mean linear velocity and Reynolds number, allowing the estimation of Darcy's friction factor and permeability.RESULTSVolumetric surface area estimated from tomography scans was ≤36% higher than the nominal values owing to surface roughness and post‐processing algorithms. By contrast, volumetric porosity obtained by tomography agreed fully with measured values. Triangular architectures afforded additional surface area both digitally and according to tomography. The largest pressure drop was found in circular materials, the triangular ones showing the lowest. The 20 ppi triangular architecture had a volumetric surface area of ≈44.5 cm−1 and a permeability of 2.31 × 10−5 cm2.CONCLUSIONTriangular architectures were preferred as a consequence of their favourable combination of high surface area and high permeability with low mass and reduced digital complexity. This provides a strategy to initiate the optimization of 3D printed porous electrodes for electrochemical flow cells and reactors in novel and niche applications. © 2021 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

A new universal model for friction factor in smooth pipes

Friction factor models for turbulent flow in smooth pipes express friction factor λ as a function of the bulk Reynolds number ReD and may be broadly grouped into two categories: power-law models and log-law models. While the former stem from the spectral scaling arguments applied to eddy momentum transfer close to the wall, the latter are derived from the mean velocity log law and are known to be consistent with the attached eddy model of wall turbulence structure. Interestingly, none of these models individually describes the entire range of Reynolds numbers (Re) accessed to date, without requiring adjustment of coefficients and/or exponents, i.e., these models are not universal. In this work, we present a new semi-empirical universal model that combines, without introducing any additional empirical coefficients, the essence of both power-law and log-law models. Due to this, our model successfully describes the variation of friction factor over the entire range of Reynolds numbers (more than four decades in ReD) at once. The physical basis for our model is the observation that at finite Reynolds numbers, the flow appears to be a small perturbation of the so-called ultimate regime of smooth-pipe turbulence, as far as friction is concerned; in the ultimate regime, λ→0 asymptotically as ReD→∞. The new model has significant potential toward accurate estimation of friction factor or flow rate in smooth pipe flows.

Numerical study on the thermo-hydraulic performance analysis of fly ash nanofluid

The heat transfer and flow characteristics of water-based fly ash nanofluid for concentrations of 0.1–1.5 vol.% that flow through a copper tube at an inlet fluid temperature of 303 K with constant heat flux boundary conditions are estimated numerically. Stability, viscosity, and thermal conductivity of fly ash nanofluid have been determined experimentally and compared with correlations available in the literature. STAR CCM + software was used to solve the governing equations using the finite volume method (FVM). Water and stable fly ash nanofluid were used as working fluids for the Reynolds number range of 4500–16,000. The Nusselt number and friction factor at 1.5% volume concentration are greater than the base fluid by 36% and 9.4%, respectively. The fly ash nanofluid showed a performance index ( $$\eta$$ ) value of more than 1 at all concentrations undertaken, indicating that the use of fly ash nanofluid in heat transfer applications is beneficial. The highest $$\eta$$ value is determined to be 1.5 approximately for a nanofluid concentration of 1.5 vol.%. The fly ash nanofluid exhibits enhanced heat transfer performance contrasted to SiO2 nanofluid. The utilization of fly ash particles for heat transfer enhancement can aid in the reduction of environmental pollution to a certain extent. Novel correlations are suggested for the estimation of fly ash nanofluid Nusselt number and friction factor.

Observer for non‐linear systems with sampled measurements: Application to the friction factor estimation of a pipeline

Observer for non‐linear systems with sampled measurements: Application to the friction factor estimation of a pipeline

Major and minor head losses in a hydraulic flow circuit: experimental measurements and a Moody’s diagram application

Domestic and industrial hydraulic drainage networks have gradually become more complicated because of the cities’ rapid expansion. In surcharged hydraulic systems, the head losses may become rather significant, and should not be neglected because could result in several problems. This work presents an investigation about major and minor head losses in a hydraulic flow circuit, simulating the water transport in a drainage network at room temperature (298.15 K) under atmospheric pressure (101,325 Pa). The losses produced by the fluid viscous effect through the one used cast-iron rectilinear pipe (RP-11) and the localized losses generated by two flow appurtenances, one fully open ball valve (BV-1) and one module of forty-four 90º elbows (90E-8) were experimentally measured. Experimental data generated head-loss curves and their well fitted to potential regressions, displaying correlation coefficients (R2) of 0.9792, 0.9924, and 0.9820 for BV-1, 90E-8, and RP-11, respectively. Head loss experimental equations and local loss coefficients through BV-1 and 90E-8 were determined successfully. The Moody’s diagram application proved to be a quite appropriate tool for an approximate estimation of Darcy-Weisbach friction factor. A good approximation between friction factor values obtained via experimental measurements and the Moody’s diagram was observed with mean absolute deviate of 0.0136.

Investigation of joint interface and cracking mechanism of thick cladding of copper on aluminum by equal channel angular pressing (ECAP)

Joint interface and cracking mechanism during thick cladding of copper on aluminum have been investigated. For this purpose, deformation of Al-Cu bimetallic inserts during equal channel angular pressing (ECAP) is investigated using finite element method (FEM). FEM results show that both metals undergo similar straining during ECAP. However, the values of maximum principal stresses that may cause cracking are significantly higher in the casing tube which continues to more significant increase by increasing number of ECAP passes. Therefore, it is concluded that cracking is likely to occur in the copper casing if ECAP deformation of the composite exceeds two passes. This is in agreement with the experimental results in which cracking is observed in the fourth pass of ECAP. Cracking in the copper casing at 45 degrees with respect to the joint interface is attributed to the existence of tensile maximum principal stresses caused by severe shear stresses at the interface. Shear bond strength between the aluminum core and the copper casing in the deformed composite increases up to 3 passes and reduces in the fourth pass. The increase is preliminary attributed to increasing the joint fraction between aluminum and copper substrates and the reduction in the fourth pass is correlated to formation of cracks on the copper substrate. Estimation of shear friction factor (m) between aluminum and copper at the joint interface indicates that it is around 0.21 independent from the number of ECAP passes. Indeed, the number of ECAP passes can change the joint surface fraction, however, it is not effective on the nature of the joint. Indeed, m smaller than 1 indicates that a solid metallurgical bonding has not formed over the joint and mechanical bonding is mostly responsible for the joint strength. In addition, as m is not a function of number of passes, it is concluded that the type of bonding at the interface is not affected by number of ECAP passes.

Investigation of the Combined Effects of Temperature and Large-Scale Tortuosity on Friction-Factor Profile in Straight Inclined Sections

Summary This paper studies the implicit effects of temperature and wellbore tortuosity on the mechanical friction factor in torque-and-drag models applied to straight inclined sections. Experimental work was performed to measure the variation of viscosity and density of a water-based-mud (WBM) sample with respect to temperature and pressure. The effect of wellbore tortuosity was accounted for by means of the dogleg-severity (DLS) filter, which is presented in the paper. Experimentally obtained parameters were included in an algorithm for friction-factor-profile back calculation using a selected torque-and-drag model. A field case is presented to show this approach. The calculated friction factors were compared with those obtained by using the original torque-and-drag model and the averaged friction-factor values provided by the field operator, and the deviation mechanisms were discussed. Comparing the obtained results, we concluded that pressure and temperature, accounted for through variation in fluid buoyancy with depth, affect friction factor just marginally for rotation off-bottom and negligibly for tripping operations. The unplanned large-scale tortuosity affects the ultimate friction factor more significantly. The magnitude of the studied effects would greatly depend on the wellbore conditions. By including additional parameters in the traditional torque-and-drag models, researchers and engineers would be able to evaluate the effects of these parameters on the friction-factor estimation. It can help to estimate the range of friction forces during the planning phase and explain abnormal trends in post-run analysis.

Effect of vegetation patches on flow structures and the estimation of friction factor

ABSTRACT In rivers, irrigation canals, and drainage channels vegetation patches often appear over the bed. Flow over vegetation patches is in non-developed region which significantly influences the flow structures, thus affecting the estimation of friction factor. In the present study, the experiments were conducted in a laboratory flume to investigate the interaction of vegetation patches with turbulent flow structures evolving area over small patches. Different roughness coefficients were applied in the presence of vegetation patches, and velocity distributions, Reynolds stress distributions, and Turbulent Kinetic Energy (TKE) distributions were analyzed because they play an important role in the estimation of friction factor. Results showed that Reynolds stress and TKE at the trailing edge of vegetation patches increased due to the vertical circulation downstream of each patch. However, the vertical circulation, Reynolds stress, and TKE decreased in the flow over three patches in comparison to the flow over two patches. Results also indicated that the geometric features of a vegetation patch played an important role in the friction factor in open channels with vegetation patches on the bed.

An evaluation of testing and modeling procedure for solids friction factor for fluidized dense-phase pneumatic conveying of fine powders

For the reliable design of a pneumatic conveying system, accurate estimation of solids friction factor through horizontal straight pipe is of paramount interest. Although the “straight pipe” method is fundamentally more appropriate, the “back calculation” approach provides several practical advantages for testing and modeling. However, earlier literature reports that “back calculation” approach suffers from 40 to 150% inaccuracy in prediction of total pipeline pressure drop in scale-up pipes, which had been discouraging for its use. In the present work, it has been argued that much of the criticism for the inaccuracy of back calculation method lies with the choice of its format of modeling solids friction factor. In this paper, “back calculation” method of modeling has been used by employing a “two layer” model format for solid friction factor for fly ash, ESP dust and cement. These models, when scaled up to predict the total pipeline pressure drop in larger and longer pipelines, have resulted in overall deviation from experimental data ranging from 3 to 35%, which is a significant improvement in prediction capability. The results prove that the selection of a better format of model for solids friction factor could significantly improve the reliability of “back calculation” method.

A new explicit friction factor formula for laminar, transition and turbulent flows in smooth and rough pipes

Pressure drop due to friction during internal pipe flow is one of the most important considerations in designing fluid and heat flow systems. There are many separate correlations valid for different situations such as laminar or turbulent rough and smooth surfaces for the estimation of friction factor. The present study introduces the derivation of a single explicit equation which is valid over the entire range of Reynolds number for both smooth and rough surfaces. This equation combines the laminar and turbulent friction factor equations through relation developed for the transition region. The results of the proposed equation were compared with the existing experimental data and the data from the Colebrook equation for smooth and rough surfaces respectively. The results show very good agreement with the experimental data as well as the Colebrook equation over the entire range of Reynold number. The percentage error lies within ± 2% and ± 10% for laminar and turbulent flows over the rough and smooth surfaces respectively.

Investigation on convective heat transfer and friction factor of silver–water nanofluid under laminar flow – an experimental study

Laminar flow forced convective heat transfer and friction factor of silver-water nanofluids were experimentally examined under uniform heat flux condition in a horizontal circular pipe. Heat transfer coefficient and friction factor of nanofluids were experimentally evaluated as a function of particle volume concentration and Reynolds number. Reynolds number was varied from 500 to 2300 for the different particle volume fraction of 0.01, 0.05 and 0.1%. The experimental results indicate that both Nusselt number and heat transfer coefficient of the nanofluid increase with the increasing particle volume concentration and Reynolds number. The maximum enhancement of 36.1% in heat transfer coefficient was obtained for 0.1% volume fraction of nanoparticles at Reynolds number of 2300. Also, there is an increase in friction factor of nanofluid with the increase in nano-particle volume concentration. New correlations of Nusselt number and friction factor of nanofluids are proposed using the experimental data. The estimation of Nusselt number and friction factor of nanofluids using the proposed correlations are in good agreement with the experimental results.

A Comparison of Data Reduction Methods for Average Friction Factor Calculation of Adiabatic Gas Flows in Microchannels.

In this paper, a combined numerical and experimental approach for the estimation of the average friction factor along adiabatic microchannels with compressible gas flows is presented. Pressure-drop experiments are performed for a rectangular microchannel with a hydraulic diameter of 295 μm by varying Reynolds number up to 17,000. In parallel, the calculation of friction factor has been repeated numerically and results are compared with the experimental work. The validated numerical model was also used to gain an insight of flow physics by varying the aspect ratio and hydraulic diameter of rectangular microchannels with respect to the channel tested experimentally. This was done with an aim of verifying the role of minor loss coefficients for the estimation of the average friction factor. To have laminar, transitional, and turbulent regimes captured, numerical analysis has been performed by varying Reynolds number from 200 to 20,000. Comparison of numerically and experimentally calculated gas flow characteristics has shown that adiabatic wall treatment (Fanno flow) results in better agreement of average friction factor values with conventional theory than the isothermal treatment of gas along the microchannel. The use of a constant value for minor loss coefficients available in the literature is not recommended for microflows as they change from one assembly to the other and their accurate estimation for compressible flows requires a coupling of numerical analysis with experimental data reduction. Results presented in this work demonstrate how an adiabatic wall treatment along the length of the channel coupled with the assumption of an isentropic flow from manifold to microchannel inlet results in a self-sustained experimental data reduction method for the accurate estimation of friction factor values even in presence of significant compressibility effects. Results also demonstrate that both the assumption of perfect expansion and consequently wrong estimation of average temperature between inlet and outlet of a microchannel can be responsible for an apparent increase in experimental average friction factor in choked flow regime.