Abstract
The critical issues are examined in the application of constant-temperature hot-wire anemometry to hypersonic boundary layers. While continuous turbulence measurements are more challenging to make in hypersonic flows, it is shown here that the difficulties can be overcome for a wide range of flow conditions. An extensive review of the literature reveals that many of the heat transfer complexities associated with hypersonic anemometry have already been resolved. Frequency-response tests, calibration results and boundary-layer measurements in hypersonic flow are also presented. A hot-wire frequency response of about 500 kHz was obtained in a Mach 11 flow, and the resulting boundary-layer spectra are smooth and repeatable.
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Abbreviations
- D :
-
hot-wire diameter
- E :
-
instantaneous anemometer voltage
- f, g :
-
functions of the overheat ratio,τ
- f r :
-
hot-wire frequency response
- g(s) :
-
dimensionless function of the molecular speed ratio
- k :
-
thermal conductivity coefficient
- l :
-
active length of the hot-wire element
- Kn :
-
Knudsen number (Kn = λ/D)
- n :
-
exponent of theNu-Re relation for a hot wire
- Nu :
-
Nusselt number
- Pr :
-
Prandtl number
- R :
-
electrical resistance
- R 1 :
-
resistance of the anemometer bridge leg in series with the wire
- Re :
-
Reynolds number based on the hot-wire diameter
- s :
-
molecular speed ratio\(\left( {{u \mathord{\left/ {\vphantom {u {V_{mp} }}} \right. \kern-\nulldelimiterspace} {V_{mp} }} = \sqrt {\frac{\gamma }{2}M} } \right)\)
- t :
-
shock thickness
- T e :
-
wire recovery temperature
- U :
-
freestream velocity
- V mp :
-
most-probable molecular speed
- α :
-
thermal accommodation coefficient
- δ :
-
boundary layer thickness or shock detachment distance
- η :
-
recovery factor (η ≡T e /T 0) or Kolmogorov length scale
- λ :
-
mean free path
- ϱ :
-
density
- τ :
-
hot-wire overheat ratio (τ ≡ (T w −T e /T 0)
- e :
-
boundary-layer edge value
- w :
-
wire value
- ∞:
-
freestream condition
- 0:
-
stagnation condition
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The work of the first author was supported by NASA-Langley Grant NAG-1-1400, under the supervision of Dr. Stephen K. Robinson. The assistance of Mr. Mark Sheplak in acquiring some of the data presented in §3 is gratefully acknowledged.
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Spina, E.F., McGinley, C.B. Constant-temperature anemometry in hypersonic flow: critical issues and Sample results. Experiments in Fluids 17, 365–374 (1994). https://doi.org/10.1007/BF01877036
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DOI: https://doi.org/10.1007/BF01877036