A Rapid Viscous-Inviscid Interaction Method for the Preliminary Design of S-Shaped Transition Ducts

2021 ◽  
Author(s):  
A. Veyrat ◽  
J. F. Carrotte ◽  
A. D. Walker ◽  
C. Hall ◽  
H. Simpson
Keyword(s):  
Shear Stress ◽  
Rapid Assessment ◽  
Layer Growth ◽  
Preliminary Design ◽  
Interaction Method ◽  
Complex Flow ◽  
Potential Core ◽  
Law Of The Wall ◽  
Streamline Curvature ◽  
Use Of Time

Abstract For preliminary design of compressor transition ducts, knowledge-based tools for the rapid assessment of aerodynamic performance of S-shaped ducts are not currently available in the open literature. This is due to the highly complex flow developing under the combined influence of pressure gradients and streamline curvature. This paper presents a new approach enabling an agile design process avoiding premature use of time-consuming high-fidelity CFD calculations. The features of a 2D axisymmetric incompressible steady flow field are captured with a semi-analytical viscous inviscid interaction method. A potential core, based on streamline curvature and implicit velocity profile by parametric spline reconstruction, is coupled to an integral method predicting the turbulent boundary layer growth up to separation. The shear stress distribution is generated by a modified mixing length model for strongly curved flows and wall shear stress closure is performed by inverse calculation of a composite law-of-the-wall. When compared to CFD, the aerodynamic loading is generally predicted to within ±3% but convergence is achieved 20 times faster.

Preston-Static Tubes for the Measurement of Wall Shear Stress

1994 ◽  
Vol 116 (3) ◽  
pp. 645-649 ◽  
Author(s):  
Josef Daniel Ackerman ◽  
Louis Wong ◽  
C. Ross Ethier ◽  
D. Grant Allen ◽  
Jan K. Spelt
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Convenient Method ◽  
Pipe Flow ◽  
Total Pressure ◽  
Static Pressure ◽  
Shear Stresses ◽  
Streamline Curvature ◽  
Syringe Needle ◽  
Wall Shear

We present a Preston tube device that combines both total and static pressure readings for the measurement of wall shear stress. As such, the device facilitates the measurement of wall shear stress under conditions where there is streamline curvature and/or over surfaces on which it is difficult to either manufacture an array of static-pressure taps or to position a single tap. Our “Preston-static” device is easily and conveniently constructed from commercially available regular and side-bored syringe needles. The pressure difference between the total pressure measured in the regular syringe needle and the static pressure measured in the side-bored one is used to determine the wall shear stress. Wall shear stresses measured in pipe flow were consistent with independently determined values and values obtained using a conventional Preston tube. These results indicate that Preston-static tubes provide a reliable and convenient method of measuring wall shear stress.

Novel Perturbation Analysis for a Widely Applicable Curvature Law of the Wall

1999 ◽  
Author(s):  
Namhyo Kim ◽  
David L. Rhode
Keyword(s):  
Perturbation Analysis ◽  
Richardson Number ◽  
Perturbation Technique ◽  
Solution Approach ◽  
Law Of The Wall ◽  
Streamline Curvature ◽  
Curvature Effects ◽  
Gradient Richardson Number ◽  
Closed Form Analytical Solution ◽  
First Time

Abstract A streamline curvature law of the wall is analytically derived to include very strong curved-channel wall curvature effects through a novel perturbation analysis. The new law allows improved analysis of such flows, and it provides the basis for improved wall function boundary conditions for their computation (CFD) over a wider range of y+, even for very strong curvature cases. The unique derivation is based on the Boussinesq eddy viscosity and curvature-corrected mixing length concepts, which is a linear function of the gradient Richardson number. For the first time, to include more complete curved flow physics, local streamline curvature effects in the gradient Richardson number are kept. To overcome the mathematical difficulty of keeping all of these local streamline curvature terms, a novel perturbation solution approach is successfully developed. This novel perturbation technique allows a closed-form analytical solution to many similar non-linear problems which previously required more complicated techniques. Qualitative and quantitative comparisons with measurements and previous curvature laws of the wall obtained by different approaches reveal that the new law shows improved representation of the wall curvature effects for all of the four test cases.

Application of Non-Linear k–ω Model to the Turbulent Flow Inside a Sharp U-Bend

2000 ◽  
Author(s):  
B. Song ◽  
R. S. Amano
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Higher Order ◽  
Shear Stresses ◽  
Complex Flow ◽  
Streamline Curvature ◽  
Non Linear ◽  
Low Reynolds

Simulation of the complex flow inside a sharp U-bend needs both refined turbulence models and higher order numerical discretization schemes. In the present study, a nonlinear low-Reynolds number (low-Re) k–ω model including the cubic terms was employed to predict the turbulent flow through a square cross-sectioned U-bend with a sharp curvature, Rc/D = 0.65. In the turbulence model employed for the present study, the cubic terms are incorporated to represent the effect of extra strain-rates such as streamline curvature and three-dimensionality on both turbulence normal and shear stresses. In order to accurately predict such complex flowfields, a higher-order bounded interpolation scheme (Song, et al., 1999) has been used to discretize all the transport equations. The calculated results by using both the non-linear k–ω model and the linear low-Reynolds number k–ε model (Launder and Sharma, 1974) have been compared with experimental data. It is shown that the present model produces satisfactory predictions of the flow development inside the sharp U-bend and well captures the characteristics of the turbulence anisotropy within the duct core region and wall sub-layer.

scholarly journals Comparison of Methods for Bed Shear Stress Estimation in Complex Flow Field of Bend

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2753
Author(s):  
Liyuan Zhang ◽  
Faxing Zhang ◽  
Ailing Cai ◽  
Zhaoming Song ◽  
Shilin Tong
Keyword(s):  
Shear Stress ◽  
Flow Field ◽  
Single Point ◽  
Three Dimensional ◽  
Bed Shear Stress ◽  
Complex Flow ◽  
Three Dimensional Flow ◽  
Stress Estimation ◽  
Log Law ◽  
Flow Field Measurement

Bed shear stress is closely related to sediment transport in rivers. Bed shear stress estimation is very difficult, especially for complex flow fields. In this study, complex flow field measurement experiments in a 60° bend with a groyne were performed. The feasibility and reliability of bed shear stress estimations using the log-law method in a complex flow field were analyzed and compared with those associated with the Reynolds, Turbulent Kinetic Energy (TKE), and TKE-w′ methods. The results show that the TKE, Reynolds, and log-law methods produced similar bed shear stress estimates, while the TKE-w′ method produced larger estimates than the other methods. The TKE-w′ method was found to be more suitable for bed shear stress estimation than the TKE method, but the value of its constant C2 needed to be re-estimated. In a complex, strong, three-dimensional flow field, the height of the measurement point (relative or absolute) should be re-estimated when a single point measurement is used to estimate the bed shear stress. The results of this study provide guidance for experimental measurement of bed shear stress in a complex flow field.

A New Streamline Curvature Throughflow Method for Radial Turbomachinery

2008 ◽  
Author(s):  
Michael Casey ◽  
Chris Robinson
Keyword(s):  
Pressure Ratio ◽  
Compressible Fluids ◽  
Preliminary Design ◽  
Streamline Curvature ◽  
Trailing Edges ◽  
Blade Row ◽  
Curved Walls ◽  
Excellent Tool ◽  
Simple Numerical Model ◽  
General Method

This paper describes a newly developed streamline curvature throughflow method for the analysis of radial or mixed flow machines. The code includes curved walls, curved leading and trailing edges, and internal blade row calculating stations. A general method of specifying the empirical data provides separate treatment of blockage, losses, and deviation. Incompressible and compressible fluids are allowed, including real gases and supersonic relative flow in blade rows. The paper describes some new aspects of the code. In particular, a relatively simple numerical model for spanwise mixing is derived, the calculation method for prescribed pressure ratio in compressor bladed rows is described, and the method used to redistribute the flow across the span due to choking is given. Examples are given of the use and validation of the code for many types of radial turbomachinery and these show it is an excellent tool for preliminary design.

Dynamics of secondary airflow and sediment transport over and in the lee of transverse dunes

2002 ◽  
Vol 26 (1) ◽  
pp. 47-75 ◽  
Author(s):  
Ian J. Walker ◽  
William G. Nickling
Keyword(s):  
Shear Stress ◽  
Sediment Transport ◽  
Conceptual Model ◽  
Research Literature ◽  
Near Surface ◽  
Law Of The Wall ◽  
Sedimentary Dynamics ◽  
Transport Patterns ◽  
And Migration ◽  
Transverse Dunes

Recent research literature on secondary airflow and sediment transport patterns over flow-transverse dunes is reviewed. Various issues surrounding the behaviour, modelling and sedimentological implications of near-surface airflow dynamics over dunes are discussed, including: the Law of the Wall; the Jackson and Hunt airflow model; the effects of streamline compression, acceleration and curvature on stoss slope shear stress; and, in particular, recent efforts to characterize secondary lee-side airflow patterns. A revised conceptual model of lee-side airflow is presented and areas for further research are identified regarding the implications of such patterns for dune sedimentary dynamics, morphology, and migration.

Wall Suction Effects on the Structure of Fully Developed Turbulent Pipe Flow

1996 ◽  
Vol 118 (1) ◽  
pp. 33-39 ◽  
Author(s):  
D. Sofialidis ◽  
P. Prinos
Keyword(s):  
Shear Stress ◽  
Pipe Flow ◽  
Stokes Equations ◽  
Turbulent Pipe Flow ◽  
Turbulent Shear ◽  
Experimental Measurements ◽  
Wall Region ◽  
Wall Suction ◽  
Law Of The Wall ◽  
Near Wall

The effects of wall suction on the structure of fully developed pipe flow are studied numerically by solving the Reynolds averaged Navier-Stokes equations. Linear and nonlinear k-ε or k-ω low-Re models of turbulence are used for “closing” the system of the governing equations. Computed results are compared satisfactorily against experimental measurements. Analytical results, based on boundary layer assumptions and the mixing length concept, provide a law of the wall for pipe flow under the influence of low suction rates. The analytical solution is found in satisfactory agreement with computed and experimental data for a suction rate of A = 0.46 percent. For the much higher rate of A = 2.53 percent the above assumptions are not valid and analytical velocities do not follow the computed and experimental profiles, especially in the near-wall region. Near-wall velocities, as well as the boundary shear stress, are increased with increasing suction rates. The excess wall shear stress, resulting from suction, is found to be 1.5 to 5.5 times the respective one with no suction. The turbulence levels are reduced with the presence of the wall suction. Computed results of the turbulent shear stress uv are in close agreement with experimental measurements. The distribution of the turbulent kinetic energy k is predicted better by the k-ω model of Wilcox (1993). Nonlinear models of the k-ε and k-ω type predict the reduction of the turbulence intensities u’, v’, w’, and the correct levels of v’ and w’ but they underpredict the level of u’.

Simplification of the Razor Blade Technique and its Application to the Measurement of Wall-Shear Stress in Wall-Jet Flows

1969 ◽  
Vol 20 (4) ◽  
pp. 355-364 ◽  
Author(s):  
B. R. Pai ◽  
J. H. Whitelaw
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Static Pressure ◽  
Jet Flows ◽  
Adhesive Tape ◽  
Wall Jet ◽  
Razor Blade ◽  
Law Of The Wall ◽  
Wall Shear ◽  
Secondary Injection

SummaryExperiments in a in (6-35 mm) channel have yielded further information on the precision and convenience of the razor blade technique. It is shown that adhesive tape or carefully located cement can be used to secure a segment of razor blade over a static pressure hole: the resulting calibration for shear stress remains valid if the blade is removed and relocated over the same or a different, similar sized hole. Razor blade segments, calibrated in this manner, have been used to measure wall-shear stress in a turbulent boundary layer with tangential, secondary injection: the results indicate that V. C. Patel’s law of the wall is valid for such flows.

The Law of the Wall for Swirling Flow in Annular Ducts

1989 ◽  
Vol 111 (2) ◽  
pp. 160-164 ◽  
Author(s):  
R. J. Kind ◽  
F. M. Yowakim ◽  
S. A. Sjolander
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Swirling Flow ◽  
Tangential Velocity ◽  
Wall Region ◽  
Law Of The Wall ◽  
Resultant Velocity ◽  
The Law ◽  
Wall Shear ◽  
Near Wall

Expressions for the logarithmic portion of the law of the wall are derived for the axial and tangential velocity components of swirling flow in annular ducts. These expressions involve new shear-velocity scales and curvature terms. They are shown to agree well with experiment over a substantial portion of the flow near both walls of an annulus. The resultant velocity data also agree with the law of the wall. The success of the proposed logarithmic expressions implies that the mixing-length model used in deriving them correctly describes flow-velocity behavior. This model indicates that the velocity gradient at any height y in the near-wall region is determined by the wall shear stress, not by the local shear stress. This suggests that the influence of wall shear stress is dominant and that it determines the near-wall wall flow even in flows with curvature and pressure gradient. A physical explanation is suggested for this.

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