Fluid Excitation Forces Acting on a Square Tube Array

1987 ◽  
Vol 109 (4) ◽  
pp. 415-423 ◽  
Author(s):  
S. S. Chen ◽  
J. A. Jendrzejczyk
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Diameter Ratio ◽  
Circular Cylinders ◽  
Incoming Flow ◽  
Test Results ◽  
Flow Conditions ◽  
Fluid Forces ◽  
System Components ◽  
Drag And Lift

Fluid forces acting on a tube array are important in the assessment of vibration of system components consisting of multiple circular cylinders. This paper presents test results for a square tube array with the pitch-to-diameter ratio of 1.75 subject to turbulent flow. The fluctuating drag and lift forces are measured as a function of Reynolds number, incoming flow conditions, and tube location in an array.

Prediction of Laminar to Turbulent Flow over a Sweptback Wing

2011 ◽  
Vol 110-116 ◽  
pp. 3473-3480
Author(s):  
Sakthivel Arumugam ◽  
Shanmugasundaram Durairaj
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Low Reynolds Number ◽  
Flow Conditions ◽  
Stability Equation ◽  
Parabolized Stability Equations ◽  
Low Reynolds

The Prediction of Laminar-Turbulent flow over wings and airfoils is necessary for low-Reynolds number airflows. The Prediction of onset of transition based on linear and Parabolized Stability Equations (PSE) using en method is reviewed and factors that influence the choice of approach are discussed. Comparison between prediction of linear and parabolized stability equation are given for a range of flow conditions on an Infinite sweptback wing.

Numerical Prediction of Turbulent Flow in Rotating Cavities

1988 ◽  
Vol 110 (2) ◽  
pp. 202-211 ◽  
Author(s):  
A. P. Morse
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Predictive Accuracy ◽  
Turbulent Transport ◽  
Reynolds Numbers ◽  
Spreading Rate ◽  
Flow Conditions ◽  
Wide Range ◽  
Ekman Layers ◽  
Radial Outflow

Predictions of the isothermal, incompressible flow in the cavity formed between two corotating plane disks and a peripheral shroud have been obtained using an elliptic calculation procedure and a low turbulence Reynolds number k–ε model for the estimation of turbulent transport. Both radial inflow and outflow are investigated for a wide range of flow conditions involving rotational Reynolds numbers up to ∼106. Although predictive accuracy is generally good, the computed flow in the Ekman layers for radial outflow often displays a retarded spreading rate and a tendency to laminarize under conditions that are known from experiment to produce turbulent flow.

Performance of a Long Smooth Multiphase Pump Seal in Different Flow Regimes

2021 ◽  
Author(s):  
Min Zhang ◽  
Dara W. Childs
Keyword(s):  
Reynolds Number ◽  
Flow Regimes ◽  
Axial Direction ◽  
Test Results ◽  
Flow Conditions ◽  
Pump Design ◽  
Multiphase Pump ◽  
Annular Seal ◽  
Oil Flow ◽  
Vibration Performance

Abstract Demanding for multiphase pumps introduces new challenges to the pump design. To prevent machine failures, the performance of the pump (non-contact) annular seal under multiphase conditions needs to be studied. The air addition into the oil flow not only changes the properties of the fluid but also can change the flow status in the seal clearance. The flow status can significantly affect the performance of the pump seal and thereby impact the pump vibration performance. Within the seal annulus, the axial direction flow is dominated by the pressure drop through the seal and can be considered as a Poiseuille flow. The circumferential direction flow is driven by the rotor rotation and can be considered as a Couette flow. The regime of the flow in the seal is controlled by the axial Reynolds number and the circumferential Reynolds number. Published test results on the boundaries between the laminar, transitional, and turbulent regimes in an annular seal are scant. This paper will first draw these boundaries based on the test data for long smooth pump seals. Then, this paper will show the performance of the long smooth pump seal in different flow regimes. Predictions will also be presented to compare with test results under different flow conditions.

Examination of Hydrodynamic Forces Acting on a Group of Circular Cylinders at High Reynolds Numbers

2016 ◽  
Author(s):  
Linwei Shen ◽  
Rajeev Kumar Jaiman ◽  
Peter Francis Bernad Adaikalaraj ◽  
Vaibhav Joshi ◽  
Jungao Wang ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Hydrodynamic Forces ◽  
Circular Cylinders ◽  
Navier Stokes ◽  
Incoming Flow ◽  
Drag Coefficients ◽  
Numerical Result ◽  
High Reynolds ◽  
Engineering Practices

A group of circular cylinders exists in many engineering practices, such as offshore drilling riser system. Due to the interference between the riser main tube and auxiliary lines, the hydrodynamic forces acting on the riser system is much different from those on a single circular cylinder. It is very rare in the publication and still not certain in the determination of the forces in the drilling riser design of the industry. Particularly, it is unclear of the hydrodynamic forces when the Reynolds number is very high which is quite common in the real ocean fields. In this paper, the stationary riser system consisting of a group of six circular cylinders with unequal diameters is considered. The hydrodynamic forces acting on the main cylinder in the Reynolds number ranging from 105 to 2×106 are numerically calculated by solving the Reynolds averaged Navier-Stokes (RANS) equations. The Spalart-Allmaras RANS model is employed to account for the turbulence effect. It is found that drag coefficients are close to 1 when the incoming flow is symmetrical with respect to the configuration of the cylinders and are dramatically reduced when the incoming flow is asymmetrical. No “drag crisis”, which is a well-known phenomenon in a single cylinder case, is found in this particular range of Reynolds numbers. A detailed analysis, including the flow field and pressure distribution around the main tube, is also presented in the present work. The numerical result of the hydrodynamic forces on the main line is very helpful for the engineers to determine the drag coefficients in the practice of drilling riser system design, under the guidance of API-RP-16Q.

Deep Learning Techniques for Effective Prediction of Aerodynamic Properties of Elliptical Bluff Bodies

2021 ◽  
Author(s):  
W. M. U. Weerasekara ◽  
H. M. C. D. B. Gunarathna ◽  
W. A. K. P. Wanigasooriya ◽  
T. P. Miyanawala
Keyword(s):  
Neural Network ◽  
Reynolds Number ◽  
Deep Learning ◽  
Aerodynamic Force ◽  
Flow Behavior ◽  
Reynolds Numbers ◽  
Bluff Bodies ◽  
Flow Conditions ◽  
Force Coefficients ◽  
Drag And Lift

Abstract Predicting aerodynamic forces on bluff bodies remains to be a challenging task due to the unpredictable flow behavior, specifically at higher Reynolds numbers. Experimental approaches to determine aerodynamic coefficients could be costly and time consuming. In the meantime, use of numerical techniques could also require a considerable computational cost and time depending on complexity of the flow behavior. The research focusses on developing an effective deep learning technique to predict aerodynamic force coefficients acting on elliptical bluff bodies for a given aspect ratio and given flow condition. Collecting data for drag and lift coefficients of several aspect ratios for flow conditions starting from onset of vortex shredding to verge of subcritical region is conducted by an accurate full order model. The specified region will provide a transient flow behavior and thus lift coefficient will be represented in terms of root mean square value and drag coefficient in terms of a mean value. With variations in flow behavior and vortex shredding frequencies, it requires to select an appropriate turbulence model, optimum discretization of fluid domain and time step to obtain an accurate result. Flow simulations are conducted primarily using Unsteady Reynolds Averaged Navier-Stokes Equations (URANS) model and Detached Eddy Simulations (DES) model. Effectiveness in using different turbulence models for specified flow regimes are also explored in comparison to available experimental results. At lower Reynolds numbers, aerodynamic force coefficients for a specified body will only depend on Reynolds number. But after a certain specific Reynolds number, aerodynamic forces are dependent on the Mach number in addition to Reynolds number. Therefore, for higher Reynolds numbers, aerodynamic force coefficients are recorded for multiple Mach numbers with same Reynolds number and will be fed to the neural network. With the development of the machine learning and neural network modelling, many of the fields have nourished and created effective and efficient technologies to ease complex functions and activities. Our goal is to ease the complexity in the computational fluid dynamic field with a deep neural network tool created to predict drag and lift coefficient of elliptical bluff bodies for a given aspect ratio with an acceptable accuracy level. Researchers have developed deep neural network tools to predict various flow conditions and have succeeded with sufficient accuracy and a satisfying reduction of computational cost. In our proposed deep learning neural network, we have chosen to model the network with inputs as the geometry setup and the flow conditions with validated drag and lift coefficients. The model will extract the necessary flow features into filters with the convolution operation performed on the inputs. Our main directive is to create a deep learned neural network tool to predict the target values within an acceptable range of accuracy while minimizing the computation cost.

The Influence of the Wall on Flow Through Pipes Packed With Spheres

1990 ◽  
Vol 112 (1) ◽  
pp. 84-88 ◽  
Author(s):  
R. M. Fand ◽  
R. Thinakaran
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Porous Media ◽  
Turbulent Flow ◽  
Porous Matrix ◽  
Circular Cylinders ◽  
Empirical Equations ◽  
Flow Parameters ◽  
Flow Through ◽  
Dimension Ratio

This paper presents the results of an experimental investigation that is a sequel to a previously published study of the flow of fluids through porous media whose matrices are composed of randomly packed spheres. The objective of the previous study was to accurately determine the ranges of the Reynolds number for which Darcy, Forchheimer and turbulent flow occur, and also the values of the controlling flow parameters—namely, the Kozeny-Carman constant for Darcy flow and the Ergun constants for Forchheimer and turbulent flow—for porous beds that are infinite in extent; that is, practically speaking, for sufficiently large values of the dimension ratio, D/d, where D is a measure of the extent of the bed and d is the diameter of a single spherical particle of which the porous matrix is composed. The porous media studied in the previous and present experiments were confined within circular cylinders (pipes), for which the dimension D is taken to be the diameter of the confining cylinder. The previous study showed that the flow parameters are substantially independent of the dimension ration for D/d ≥ 40. For D/d < 40, the so-called “wall effect” becomes significant, and the flow parameters become functionally dependent upon this ratio. The present paper presents simple empirical equations that express the porosity and the flow parameters as functions of D/d for 1.4 ≤ D/d < 40. Transitions from one type to another were found to be independent of D/d and occur at values of the Reynolds number identical to those reported in the previous study.

Vortex Shedding with Fluid Mechanics from Two Cylinders of Different Diameters in a Tandem Arrangement

2014 ◽  
Vol 886 ◽  
pp. 436-439
Author(s):  
Yong Tao Wang ◽  
Zhong Min Yan ◽  
Hui Min Wang
Keyword(s):  
Reynolds Number ◽  
Fluid Mechanics ◽  
Vortex Shedding ◽  
Diameter Ratio ◽  
Circular Cylinders ◽  
Tandem Arrangement ◽  
Gap Ratio ◽  
Different Diameters ◽  
Upstream Control ◽  
Control Cylinder

The vortex shedding from two circular cylinders of different diameters in a tandem arrangement is numerically investigated at a Reynolds number of 100 and 150. The studied Reynolds number based on the diameter of the downstream main cylinder. The diameter of the downstream main cylinder was kept constant, and the diameter ratio between the upstream control cylinder and the downstream one was varied from 0.1 to 1.0. The gap between the control cylinder and the main cylinder ranged from 0.1 to 4.0 times the diameter of the main cylinder. It is concluded that the gap ratio and the diameter ratio between the two cylinders have important effects on vortex shedding from two cylinders of different diameters in a tandem arrangement.

scholarly journals Fluctuating Fluid Forces Acting on Two Circular Cylinders in a Tandem Arrangement at a Subcritical Reynolds Number

2001 ◽  
Vol 2001 (89) ◽  
pp. 697-724
Author(s):  
M. Moriya ◽  
Md. Mahbub Alam ◽  
K. Takai ◽  
H. Sakamoto ◽  
Masaru MATSUMOTO ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Circular Cylinders ◽  
Tandem Arrangement ◽  
Fluid Forces

Experimental Study and Detached Eddy Simulation of the Macro-Instability in an Eccentric Stirred Tank

2011 ◽  
Vol 66-68 ◽  
pp. 20-26 ◽  
Author(s):  
Feng Ling Yang ◽  
Shen Jie Zhou ◽  
Gui Chao Wang
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Simulation Method ◽  
Dominant Frequency ◽  
Diameter Ratio ◽  
Stirred Tank ◽  
Detached Eddy Simulation ◽  
Rushton Turbine ◽  
Eddy Simulation ◽  
Tank Diameter

The turbulent flow in stirred tank is highly complicated and anisotropic, especially when the macro-instability (MI) are involved. In this work, the numerical simulation method of the eccentric agitation was established based on the detached eddy simulation (DES) model to study the MI in an eccentric stirred tank. The turbulent flow in the eccentrically located Rushton turbine stirred tank was numerically investigated. The rotation of the impeller was simulated by the transient sliding mesh (SM) method. The effect of eccentricity, impeller Reynolds number and impeller-tank diameter ratio were studied in order to quantify the MI frequency. PIV experiments were performed to validate the DES results and frequency analyses were applied to the obtained time series of the velocity recordings. It was found that the flow field in eccentrically stirred tank are highly unsteady and is subject to MI with varying period less than 10 blade passage period. Good agreements have been found between the DES and PIV results, both indicate that the dominant frequency of MI increases linearly with the Reynolds number, increases with the impeller-tank diameter ratio and decreases with the eccentricity. According to the agreements between the experimental and simulation results, it can be concluded that the combination of DES and SM is suitable for the prediction of the MI phenomenon in stirred tanks.

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