An investigation of the effects of heat transfer on boundary-layer transition on a parabolic body of revolution (NACA RM-10) at a Mach number of 1.61 Page: 3 of 12

                                
EFFECTS OF HEAT TRANSFER ON BOUNDARY-LAYER TRANSITION ON A PARABOLIC BODY OF REVOLUTION  931

Typical thermocouple knstallation---

in.

r-Threaded interior
/

Coolant spray tubes-A
(replaceable by heating element)

Schleren

Liquid C02 supply

Termocouple location
Station, Number Spailng,
in.              deg
3.0      2       180
12.6      2      180
22.4      4       90
32.0      2      180
37.1      2      180
46.O      2      180
FIaREn 2.--Sketch of NACA RM-10 model and apparatus for heating and cooling. Model length, 50.0 inches;
maximum diameter, 4.096 inches.

Ir-          YY                              -CI
FIGURE 3.-NACA RM-10 modeL
these tubes to act as spray orifices. The inside of the model
was deeply grooved, wherever possible, to increase the
exposed surface area and to induce turbulence in the heating
or cooling gas flow so that a high rate of heat transfer would
be favored. Supply lines for the spray tubes were brought
through the base of the model on the outside of the sting.
For phase II of the investigation, the cooling system re-
mained unchanged, but the steam heating system was re-
placed by an electrical heating element consisting of a steel
rod wound with heavy resistance wire, capable of operation
to 1600 watts. Power input to the heating element was
controlled by means of a Variac.
The model was mounted on a sting in the tunnel and an
electrical strain-gage balance was mounted in the rear part
of the model. This balance was operative only during phase

F           _-                                        1

H-
L-75138
FIoGi  i--Model base showing details of boundary-layer survey
rake.
II of the investigation. Fourteen iron-constantan thermo-
couples were installed in the surface of the model as shown
in figure 2, and the leads were brought out through the base
of the model on the outside of the sting.
Boundary-layer profiles were determined by means of a
rake of tubes shown in figure 4. The rake was constructed
of fifteen total-pressure tubes and two static-pressure tubes
with a 0.040-inch outside diameter (0.030-inch inside diam-
eter) chosen to meet response-time requirements, and the
ten total-pressure tubes closest to the surface were flattened
to a height of about 0.025 inch per tube to give closer spacing.
The rake was clamped on the sting so that boundary-layer
profiles were determined about R4 inch ahead of the base of
the model. Sheet-metal spacers were wedged between the

X

Welded

"4         V'~~~~~''''~~~:

i-71.7

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