The motive force driving the fluid out of the cup is the head of fluid, which is also contained within the equation that makes up the volume of the fluid. Kinematic viscosity value of the fluid in Centistokes (cSt). The timings can be used in a formula to estimate the Viscosity can be measured by timing the flow of a known volume of fluid from a This value must be converted back to 1.002 x 10^-3 Pa Temperature of 20☌ has a viscosity of 1.002 Centipoise. Pascals can be combined with time (seconds) to define dynamic viscosity.Ĭentipoise (cP) is commonly used to describe dynamic viscosity because water at a The Pascal unit (Pa) is specifies pressure, or stress = force per area Laminar flow will occur where the Reynold's number is less than 2300.įrom the above equation it can be determined that the dimensions of viscosity are force multiplied by time divided by length squared or FT/L² The units of viscosity in the English system and the SI system are: To determine whether the flow is laminar or turbulent requires that you calculate the Reynold's number of the flowing fluid. However, the above equation is not applicable for turbulent flow where a large amount of the shear stress is due to the exchange of momentum between adjacent layers of the fluid. This results in the important equation for fluid shear for viscous or laminar flow: The derivative dv/dy is called the velocity gradient. Viscosity is usually denoted by the Greek symbol μ (mu) and is defined as the ratio of shearing stress τ (Greek letter tau) to the rate of change of velocity, v, which in mathematical terms can be expressed as dv/dy (where this is the derivative of the of the velocity with respect to the distance y). s/m²), η₂ is the viscosity at 99☌ (0.Fluid Viscosity Properties Fluid Viscosityįluid Viscosity, sometimes referred to as dynamic viscosity or absolute viscosity, is the fluid's resistance to flow, which is caused by a shearing stress within a flowing fluid and between a flowing fluid and its container.Where η is the viscosity at 60☌, η₁ is the viscosity at 38☌ (0.067 N To find the viscosity of SAE 0W-30 motor oil at 60☌ using interpolation, we can use the following equation: s/m²), T₁ is the initial temperature (158☌), η₂ is the dynamic viscosity at 200☌, T₂ is the final temperature (200☌), and C is Sutherland's constant (120 K for air).To find the viscosity of air at 200☌ using Sutherland's equation, we can use the following formula: Then, we can calculate the change in viscosity and density using the above equations. To find the change in viscosity and density of water and air between 10☌ and 70☌, we can use the following equations:įor water and air, we can find the values of viscosity and density at 10☌ and 70☌ from standard tables or online resources. Where g is the acceleration due to gravity (9.81 m/s²). The specific weight (γ) of carbon dioxide can be calculated using the formula: We are given P = 300 absolute (assuming this is in kPa) and R = 8.314 J/(mol Now, we can use the ideal gas law equation to find the density (ρ) of carbon dioxide: Where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature in Kelvin.įirst, convert the temperature to Kelvin: 1- To calculate the specific weight, density, and pressure of carbon dioxide at 300 absolute and 608☌, we need to use the ideal gas law equation:
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