In a particular flow field, if the temperature probe is designed such that heat loss from the sensor is negligible, then the value of K is equal to R as it is the measure of transport phenomena in the boundary layer and it gets altered by the shape of the instrument. The various temperature discussed above in a compressible flow is shown in Fig. 7.5.2.

When the measurement is performed for supersonic flow stream, a detached shock is formed at a certain distance in front of the probe (Fig. 7.5.3). Since the flow across a shock is adiabatic, the stagnation temperatures remain the same before and after the shock. So, the temperature measurement remains unaffected.

 

Fig. 7.5.2: Representation of temperature trends in a compressible flow.

Fig. 7.5.3: Detached shock ahead of the measuring temperature probe in a supersonic flow.