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# pressure

Compute the pressure due to a volume of gas.
Controller: lodmore
Contents

C++
Excel

## Pressure

 doublepressure( double p1 double v1 double v2 double gamma = 1.4 )
Compute the pressure due to a change in volume of gas, based on the adiabatic expansion
$p_1&space;v_1^\gamma&space;=&space;p_2&space;v_2^\gamma$

Therefore
$p&space;_1=&space;p_2&space;\frac{v_2}{v_1}^\gamma$

where γ is the gas constant, equal to 1.4 for air.

### Example 1

The follow graph show the change pressure when an initial 2m3 air is expanded or contracted:
There is an error with your graph parameters for pressure with options v1=2 p1=14.7 v2=0.1:4

Error Message:Function pressure failed. Ensure that: Invalid C++

### Note

The units for pressure and volume can be interchanged with SI or Imperial systems, so long as the units used for p1 are the same as those in p2; and equally the units of v1 = v2. i.e. You are consistent.

### Parameters

 p1 The initial pressure [psi] v1 The initial volume [ft3] v2 The new volume [ft3] gamma The gas constant. Default value = 1.4 (for air)

### Returns

The new pressure at volume v2. [psi]

### Authors

James Bateman (March 2008)
##### Source Code

Source code is available when you agree to a GP Licence.

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