Method and apparatus for measuring the permeability to water of pervious sheets

In a method for the measurement of the permeability to water of a pervious sheet material, which method provides a reduced washing effect of the water flow on the pervious sheet material and a permeability measurement of enhanced dynamics, comprising the steps of:

• 1) regulating a flow of water in a water line to produce a flow of water having a constant volume rate of flow;
• 2) introducing a gas into the water flow to obtain a mixture of the water flow having a constant volume rate of flow and gas;
• 3) providing the mixture of the gas and the water flow having a constant volume rate of flow through the water line to a nozzle;
• 4) placing the nozzle against one surface of the pervious sheet material;
• and
• 5) measuring the permeability of the pervious sheet material by measuring the pressure of the mixture of the water flow having a constant volume rate of flow and gas in the nozzle.

In a method for the measurement of the permeability to water of a pervious sheet material providing a reduced washing effect of the water flow on the pervious sheet material and a permeability measurement of enhanced dynamics, comprising the steps of:

• 1) regulating a flow of water in a water line to produce a flow of water having a constant volume rate of flow;
• 2) introducing a gas into the water flow by using a means (8) for introducing gas into the flow of water in the liquid flow line (2), comprising an inlet duct (9) for the gas surrounded by an opening (10) for the liquid flow line (2), debouching in a mixing zone (11), an annular edge (13) being provided in the mixing zone (11) whereby gas is entrained from the inlet duct (9) into the liquid flow line (2) to obtain a mixture of the water flow having a constant volume rate of flow and gas;
• 3) providing the mixture of the water flow having a constant volume rate of flow and gas through the water line to a nozzle;
• 4) placing the nozzle against one surface of the pervious sheet material;
• and
• 5) measuring the permeability of the pervious sheet material by measuring the pressure of the mixture of the water flow having a constant volume rate of flow and gas in the nozzle.