Testing of Unpowered Advanced Underwater Vehicles at Very High Reynolds Numbers

1982 ◽  
Vol 19 (4) ◽  
pp. 339-340 ◽  
Author(s):  
A. Wortman
Keyword(s):  
Reynolds Numbers ◽  
Underwater Vehicles ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
Very High

Turbulent boundary layer statistics at very high Reynolds number

2015 ◽  
Vol 779 ◽  
pp. 371-389 ◽  
Author(s):  
M. Vallikivi ◽  
M. Hultmark ◽  
A. J. Smits
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
High Reynolds Number ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Mean Velocity ◽  
High Reynolds Numbers ◽  
Layer Flow ◽  
High Reynolds ◽  
Very High

Measurements are presented in zero-pressure-gradient, flat-plate, turbulent boundary layers for Reynolds numbers ranging from $\mathit{Re}_{{\it\tau}}=2600$ to $\mathit{Re}_{{\it\tau}}=72\,500$ ($\mathit{Re}_{{\it\theta}}=8400{-}235\,000$). The wind tunnel facility uses pressurized air as the working fluid, and in combination with MEMS-based sensors to resolve the small scales of motion allows for a unique investigation of boundary layer flow at very high Reynolds numbers. The data include mean velocities, streamwise turbulence variances, and moments up to 10th order. The results are compared to previously reported high Reynolds number pipe flow data. For $\mathit{Re}_{{\it\tau}}\geqslant 20\,000$, both flows display a logarithmic region in the profiles of the mean velocity and all even moments, suggesting the emergence of a universal behaviour in the statistics at these high Reynolds numbers.

The Importance of Secondary Shedding in Two-Dimensional Wake Formation at Very High Reynolds Numbers

1982 ◽  
Vol 33 (2) ◽  
pp. 105-123 ◽  
Author(s):  
P.K. Stansby ◽  
A.G. Dixon
Keyword(s):  
Vortex Method ◽  
Reynolds Numbers ◽  
Discrete Vortex ◽  
Pressure Distributions ◽  
Pressure Fields ◽  
High Reynolds Numbers ◽  
First Approximation ◽  
High Reynolds ◽  
Very High ◽  
Good Agreement

SummaryUncertainties in the use of the discrete-vortex method in modelling the time development of the wake of a circular cylinder at very high Reynolds numbers are investigated. It is shown that simply introducing vorticity at generally accepted separation positions at a rate of ½Us2, Us being the velocity at separation, gives wholly unrealistic wake predictions. In the base region pressure fields occur which would promote separation in steady flow and so a first approximation for ‘secondary’ separation is incorporated into the model. This brings pressure distributions and vorticity structures at subcritical and supercritical Reynolds numbers into good agreement with experiment. The convection of the vortices is calculated using the cloud-in-cell technique and comparisons are made with direct summation methods.

SOME REMARKS ON THE COMPUTATION OF THE EIGENVALUES OF LINEAR SYSTEMS

1991 ◽  
Vol 01 (02) ◽  
pp. 153-165 ◽  
Author(s):  
A.A. ABDULLAH ◽  
K.A. LINDSAY
Keyword(s):  
Spectral Analysis ◽  
Linear Systems ◽  
Spectral Methods ◽  
Stability Theory ◽  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
Sommerfeld Equation ◽  
Very High

This paper has been prompted by some recent computations of eigenvalues of the Orr-Sommerfeld equation for very high Reynolds numbers. We have used a spectral analysis to emulate these calculations and our results have motivated some general remarks on the suitability of tracking and spectral methods as numerical eigenvalue schemes in the context of stability theory. Our remarks are further supported by illustrating the development of eigenvalues in the Magnetic Benard.

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