04 Atkinson Eq Square Law Friction&Shock Loss

Atkinson EquationFriction Loss and Shock Loss

Nuhindro Priagung Widodo

Teknik PertambanganFakultas Teknik Pertambangan dan Perminyakan

Institut Teknologi Bandung 2014

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Rational Turbulent Resistance, Rt

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Frictional pressure drop

Turbulent Resistance

Correction for density ≠ 1.2 kg/m3

Atkinson Equation and Square Law

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Chezy Darcy’s Equation

Atkinson’s Equation

Atkinson friction factor

Square Law

Atkinson Resistance

Assumption: air density constant, usually basis on standard density of air, , 1.2 kg/m3

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Shock LossWhenever the airflow is required to change direction, additional vortices will be

initiated. The propagation of those large scale eddies consumes mechanical energy (shock losses) and, hence, the resistance of the airway may increase significantly. This occurs at bends, junctions, changes in cross-section, obstructions, regulators and at points of entry or exit from the system.

The effects of shock losses remain the most uncertain of all the factors that affect airway resistance. This is because fairly minor modifications in geometry can cause significant changes in the generation of vortices and, hence, the airway resistance. Analytical techniques may be employed for simple and well defined geometries. For the more complex situations that arise in practice, scale models or computational fluid dynamics (CFD) simulations may be employed to investigate the flow patterns and shock losses.

There are two methods that may be used to assess the additional resistance caused by shock losses.

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