Study regarding the constants of the logarithmic law of the wall on the basis of measurement results
Abstract
If the constants kappa and C in the logarithmic law of the wall are considered to be universal, it is possible to determine the local wall shear stress on the basis of boundary layer measurements. If the obtained wall shear stress is employed in von Karman's momentum equation and both sides are separately integrated over the flow path under conditions which neglect the terms of fluctuation, it is found that, particularly in the case of delayed flows, there are often great differences regarding the right and the left side of the equation. In the considered investigation, the wall shear stress data for all experimental data summarized at the Stanford Conference 1968 are determined by means of von Karman's momentum equation. In the investigation, it is assumed that the left side of the momentum equation provides the true wall shear stress. The obtained results show that assumptions regarding a constancy of kappa and C are not justified and that the value of kappa and C varies as a function of the positional coordinate in the flow direction.
 Publication:

Deutsche Gesellschaft fuer Luft und Raumfahrt
 Pub Date:
 May 1981
 Bibcode:
 1981dglr.meetR....P
 Keywords:

 Boundary Layer Flow;
 Flow Measurement;
 Shear Stress;
 Wall Flow;
 Differential Equations;
 Flow Velocity;
 Logarithms;
 Numerical Integration;
 Von Karman Equation;
 Fluid Mechanics and Heat Transfer