• Version
• 172 Downloads
• 3.43 MB File Size
• 1 File Count
• September 7, 2016 Create Date
• September 7, 2016 Last Updated

National Advisory Committee for Aeronautics, Report - An Experimental Investigation of Transonic Flow Past Two Dimensional Wedge and Circular Arc Sections Using a Mach Zehnder Interferometer

Interferometer measurements are given of the flow fields near
two—dimensional wedge and circular-arc sections at zero angle
of attack at high-subsonic and low-supersonic velocities. Both
subsonic flow with local supersonic zone and supersonic flow
with detached shock ware hare been inrestigated. Pressure
distributions and drag coeficients as functions of Jfach number
hare been. obtained. The wedge data are compared with the
theoretical work on flow past wedge sect-ions of Guderley and
Yoshihara. Vincent-i and Wagoner, and Cole.

It is shown that the local fliach number at any point on the
surface of a finite three-dimensional body or an unswept two-
d-imensional body. moving through an infinite fluid, has a
stationary mine at M'ach number I and. in fact, remains nearly
constantfor a range of speeds below and abore .lIach number I.
On- the basis of this concept and the experimental data, pressure
distributions and drag coeficientefor the u—edge and circular—arc
sect-ions are presented throughout the entire transonic range of
relocities.

The difficulties inherent in studying transonic flow are
well—known; Theoretical analysis is made dificult by the
nonlinearity of the differential equations of compressible
fluid motion. This nonlinearity leads to a change—over in
type of the differential equationsme elliptic to hyper-
bolic when transition is made from subsonic to supersonic
speeds. Since the essential feature of transonic flow is this
mixed subsonic-supersonic character, it, is obvious that no
linearization of the differential equations (at least in the
physical plane) can adequately describe the flow.

In this paper it is shown that in many instances tests need
not be made in the region very close to JI,=1 since the
flow in this range can be inferred from testing below and
above this range and using an interpolation based on the
fact that the local Mach number at- any point on the surface
of unswept two-dimensional bodies and finite three-dimen-
sional bodies has a stationary value at JI.=1.