Monometer CFD Simulation by Ansys Fluent, Training

Monometer Project Description

In this project, we study a Monometer CFD Simulation by Ansys Fluent, and it has been shown how there is variation in U-tube manometric fluid column. The multiphase  VOF model has been used. A convergent and divergent nozzle has been used to create a pressure difference. One end of the manometer is attached at the throat, and the other at the converging section. There is a rise in the liquid column in the U- tube manometer at the low-pressure region.

Monometer CFD Simulation by Ansys Fluent

Manometers are pressure measurement devices that are commonly used in everyday life. For example, pressures in piping systems are constantly monitored using these devices. The U-tube manometer is a special manometer that gets its name from its U-shaped tube. The straight portions of this U are commonly referred to as the manometer’s arms, limbs, or ends. The manometer is typically filled with a dense, colored fluid called the manometer fluid, which is used to visualize the pressure difference between the two ends of the tube. As the pressure at one of its ends increases, the manometer fluid inside the tube is pushed downward at that end.

This causes the manometer fluid to rise at the other end of the device. The difference in the fluid levels between the two ends is then used to measure the pressure difference. When used properly, the manometer, one of the earliest pressure-measuring instruments, is very accurate.   The manometer has no moving parts subject to wear, age, or fatigue. Manometers operate on the Hydrostatic Balance Principle: a liquid column of known height will exert a known pressure when the weight per unit volume of the liquid is known.

Geometry & Mesh

The 2-D geometry of the present model is generated using Design Modeler software.

The meshing of the present model has been done using Ansys Meshing software. The mesh type is unstructured in all of the computational domains, and the element number is equal to 42413.

CFD Simulation

To simulate the present model, we consider several assumptions:

• The solver is pressure-based.
• The current simulation is unsteady in terms of time.
• The gravity effect is equivalent to -9.81 m.s-1.

Here is a summary of the steps for defining the problem and its solution in the following table:

Models
Multiphase
	Homogeneous model	Volume of fluid
	Number of Eulerian phases	2(air& mercury)
	Interface modeling	Sharp
	Formulation	explicit
	Body force formulation	Implicit body force
Viscous model		k-epsilon
Material Properties
Air
	Density	1.225
	viscosity	1.7894e-05
mercury
	Density	13529
	viscosity	0.001523
Boundary conditions
Inlet air			Velocity inlet
		volume fraction	1
		velocity magnitude	1.8 m.s-1
Outlet		Pressure outlet
	gauge pressure	0 Pascal
	air backflow volume fraction	0
Solution Method
Pressure-velocity coupling		Piso
Spatial discretization	pressure	presto
	momentum	first-order upwind
	Volume fraction	Geo reconstruct
	Turbulent kinetic energy	First-order upwind
	Turbulent dissipation rate	First-order upwind
Initialization
Initialization method		Standard
Patch	Phase	air
	Variable	Volume Fraction
	Registers to patch	region_0
	Value	0
Run calculation
Time step size		0.001
Max iterations/time step		10
Number of time steps		1200

Monometer Results

First, a volume fraction diagram was drawn in different positions in this simulation. Then two-dimensional contours related to density, streamline, air volume fraction and mercury volume fraction were obtained. The images show that Initially, the height of the liquid column is equal on both sides. But as the gas enters the manometer, the height of the mercury column changes.