IntroductionInterest in the direct measurement of the shear force in a fluid in motion along an element of wall has been Direct Shear-Force shown many timesR] in cases ofboth incompressiblelli and compressible flows, and in the case of turbulent bound-NM easuremnent on ary layers in particular. [Y] ,] This measurement is even more interesting in hyper-Small Surface sonic flows because of the difficulty of applying the usual methods of probing when there are real gas effects.[5
ElementsBut there is not any solution yet, as far as we know, that is altogether satisfactory for such measurement under the conditions usually found in hypersonic wind JEAN-PIERRE CHEVALLIER tunnels. Therefore, we have tried to design and build a ONERA pickup that has the sensitivity and the response time 92 Chatillon, France necessary to permit direct measurement of the shear force on small elements of surface under the conditions particular to the hot-shot wind tunnels. In the solutions retained, the element of surface is fixed on elastic blades and its displacement is detected by variations of induc-Abstract tion in coils; this principle is well known and therefore An instrument for measuring shear forces in hypersonic wind-tunnel will not be described at length; we will concentrate inflow is described. Unique mechanical deflection-spring applications stead upon the behavior of the kinematics of V-shaped with inductive displacement pickups are used. The ability to analyze blades which, although conventionalM21 and particularly and remove the unwanted effects is demonstrated for the novel design appropriate for such a pickup, have not been, to our concept. knowledge, utilized for such a purpose.
