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→How to measure total energy
As outlined above, the problem of total energy compensation boils down to the problem of finding a location on the aeroplane where the pressure coefficient is -1. This is, however, not easy. We can get around this problem by designing a device which '''produces''' this pressure coefficient, just like a pitot tube is designed to produce a pressure coefficient of +1. This device is known as a total energy tube or total energy probe. There are mainly two kinds of architectures: the Venturi type (found on HTV) and the cylindrical type (found on KFY, JEC, PZ, and some other gliders at GRL).
[[File:venturi_tube.png|200px|thumb|right|Schematic of a Venturi tube]] On the right is a schematic drawing of a Venturi tube<ref>https://i1.wp.com/vakratoond.com/wp-content/uploads/2015/12/281.png</ref>. In order not to bore the reader, the detailed mathematics is not shown here, but for this to work, the required area ratio is: \[ \frac{A_2}{A_1} = \frac{1}{\sqrt{2}} \] Measuring the pressure at point 1 (\(p_1\)) and point 2 (\(p_2\)) and subtract them, \(p_2-p_1\) gives a pressure coefficient of -1. In reality, the area ratio needs to be slightly different to correct for viscous effects which is not included in the derivation. A variant of this type of total energy tube, namely the Orifice type, is also suitable and probably easier to manufacture. The drawback of a Venturi in measuring the total energy is that it is not tolerant to yaw. Most of the time when the total energy will be of interest is when the glider is soaring, and continuous turning is usually included in this process. If the glider has some yaw, the air will not enter the Venturi in the correct direction but it needs to turn a bit. This changes the pressure in the Venturi and leads to unreliable readings. A more benign design is the cylinder type.
=== Variometer (gliders) ===