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Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure the "accessible void", the total amount of void space accessible from the surface (cf. closed-cell ...
LVF – Liquid volume fraction is the ratio of the liquid volumetric flow rate to the total volumetric flow rate. Hold up is the cross sectional area occupied by the liquid in the pipe carrying the wet gas flow. Void fraction is the ratio of the flow area occupied by the gas to the total flow area. Lockhart–Martinelli parameter. [5]
At the microscopic and macroscopic levels, porous media can be classified. At the microscopic scale, the structure is represented statistically by the distribution of pore sizes, the degree of pore interconnection and orientation, the proportion of dead pores, etc. [4] The macroscopic technique makes use of bulk properties that have been averaged at scales far bigger than pore size.
There are different flow patterns detected as a cavitation flow progresses: inception, developed flow, supercavitation, and choked flow. Inception is the first moment that the second phase (gas phase) appears in the system. This is the weakest cavitating flow captured in a system corresponding to the highest cavitation number. When the cavities ...
The global proportionality constant for the flow of water through a porous medium is called the hydraulic conductivity (K, unit: m/s). Permeability, or intrinsic permeability, ( k , unit: m 2 ) is a part of this, and is a specific property characteristic of the solid skeleton and the microstructure of the porous medium itself, independently of ...
Void content in composites is represented as a ratio, also called void ratio, where the volume of voids, solid material, and bulk volume are taken into account.Void ratio can be calculated by the formula below where e is the void ratio of the composite, V v is the volume of the voids, and V t is the volume of the bulk material.
The reasoning for the definition of the ranges is as follows (typical circumstances): Prevailing atmospheric pressure (31 kPa to 110 kPa) to 100 Pa low (rough) vacuum Pressure can be achieved by simple materials (e.g. regular steel) and positive displacement vacuum pumps; viscous flow regime for gases <100 Pa to 0.1 Pa medium (fine) vacuum
where is the void ratio, is the porosity, V V is the volume of void-space (gases and liquids), V S is the volume of solids, and V T is the total (or bulk) volume. This figure is relevant in composites , in mining (particular with regard to the properties of tailings ), and in soil science .