what should be the flow situation for locating pressure and velocity probe? I mean what should be the boundary layer situation for having the best place to locate these probes?
regards
If they are intended for boundary layer surveys , I would traverse the probes all the way down to one probe diameter close to the wall. One needs to be cautious for wall proximity errors that may be induced by the local flow between the probe and the nearby wall. Because of the existence of a solid wall near one side of the probe, experimental errors may be high in this channel flow area.Sub-miniature probes are essential in boundary layers with small thickness. If the measurement is geared towards the region outside the boundary layer, I would go at least 2 boundary layer thickness away from the wall to avoid wall proximity effects.
Dear Masoud,
It would be helpful to know whether it is a steady or unsteady flow, and whether you wish to measure the velocity or pressure profile in the vertical direction or an average velocity. Besides what are your measurement instruments? The ADVs from Nortek or Sontek measure the velocity in three directions. The instruments are capable of measuring the velocities very close to the boundaries.
Dear Mahmoodian you can download my paper in my researchgate in which i explain about the procedur of data collection by Conductivity double-tip probe that i invent for the first time in Iran.
This depends what sort of application you have in your mind. If it is a complex flow field, I suggest you first get a feel for it through pilot experimentation or even through simple CFD, which will not be very accurate but will give you reasonable information to decide probe location for actual measurement.This will give you an idea of gradients etc and allow you to develop an improved measurement system for accurate flow information. Please read one of my papers on how to place a five hole prove in a wheel arch for accurate measurements in 'advances in mechanical engineering'.
1. Theory and usage of a pitot tube: Consult an experimental fluid dynamics handbook, e.g., Goldstein, ed. (1984) or Tropea et al., eds. (2007). These also cover other flow measurement techniques, in case a pitot tube was not what you were referring to.
2. For boundary layer measurements, e.g.: Bailey et al. (2013) Obtaining accurate mean velocity measurements in high Reynolds number turbulent boundary layers using Pitot tubes. Journal of Fluid Mechanics, 715 . pp. 642-670.
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