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The description of the fluid flow solution in a nozzle
Říha, Zdeněk
The description of the fluid flow solution in a nozzle with help of ANSYS-Fluent software is listed in this article. Self-oscillations of the main hydraulic parameters are consequence of the fluid flow in the nozzle. Input pressure of the water reaches level 10 MPa. This value evokes high speed fluid flow in the nozzle. Fluid is created with the mixture of water air and vapor. For such conditions, we need to take into account the effect of compressibility in the calculation. The aim of the calculations was to find a principal of the flow in the nozzle for given conditions, if we know, that in fact a pulsating fluid jet was at the output form the nozzle
Fulltext: content.csg -  PDF
Plný tet: UGN_0426588 - PDF
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CFD code as a helper for the design of the water jet cutting device
Říha, Zdeněk
The efficiency of the amplification of high pressure pulsations in the geometric transition between larger and smaller pipes is analysed in this paper. Three types of geometric transitions are compared in the paper: step change, conical and radius change of pipe diameters. In other words, water flow in a device for water jet cleaning and cutting is evaluated. There are ultrasonic pulsations of high pressure in the given domain.
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Ultrasonic pulsations of pressure in a tool for water jet cutting
Říha, Zdeněk ; Foldyna, Josef
Water flow in a tool for water jet cleaning and cutting is evaluated in this paper. There are ultrasonic pulsations of high pressure in the given domain. The efficiency of the amplification of high pressure pulsations in the transitional space between larger and smaller pipes is analysed. Three types of transitional spaces are compared in the paper: step change, conical and radius change of pipe diameters.
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Forces and Moments in CFD Analysis
Říha, Zdeněk ; Foldyna, Josef
The paper shows how to find the force point of action, when we know the total force and the total moment. It is usual case if we solve fluid flow with help of a CFD code. Correct interpretation of force´s act is very important for next possible analysis.
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Study of propagation of pressure pulsations in high-pressure system
Foldyna, Josef ; Říha, Zdeněk ; Sitek, Libor
Various alternatives of high pressure-system geometry including square elbows and prolongation of liquid waveguide were elaborated to be able to simulate real tools used to generate high-speed water jets. Variable geometrical parameters of the model were selected and the computational model was prepared in such a way that the geometry and meshing of the model is generated automatically after entering the parameters. This approach facilitates and speeds up preparation of models for simulation of propagation of pressure pulsations in high-pressure system for generation of pulsating water jets. The paper presents results of simulation of propagation of pressure pulsations through various geometries of the high-pressure system.
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Calculation of natural frequency of high-pressure system
Foldyna, Josef ; Říha, Zdeněk ; Sitek, Libor
The paper presents results of numerical simulation of 3D, unsteady, turbulent flow of compressible water in a high-pressure system equipped with acoustic generator of pressure pulsations and its response to a pressure impulse. Results of numerical simulation are compared to the laboratory measurement of response of high-pressure system to a pressure impulse using dynamic pressure sensor placed upstream to the nozzle exit.
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Simulation of transmission of pressure pulsations in high-pressure system
Foldyna, Josef ; Říha, Zdeněk ; Sitek, Libor ; Švehla, B.
The paper presents results of numerical simulation of 3D, unsteady, turbulent flow of compressible water in a high-pressure system equipped with an acoustic generator. The generator vibrates at frequency of 20 kHz with amplitude of 6 µm. Acoustic waves (pressure pulsations), generated in water pressurized to 30 MPa and amplified by appropriately designed liquid waveguide, results in generation of very high velocity pulsations at the nozzle outlet. The influence of various geometrical configurations on acoustic wave propagation in the high-pressure system was simulated and results were verified by laboratory measurement of pressure pulsations upstream to the nozzle exit.
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Flow in the nozzle with moving wall
Foldyna, Josef ; Říha, Zdeněk ; Sitek, Libor
The paper presents simulation of 3D, unsteady, turbulent flow of water in the high-pressure nozzle device with moving wall. The wall performs rectilinear reciprocating motion with high frequency and very small amplitude that results in generation of very high velocity pulsations at the nozzle outlet. The pulsations lead to the break-up of continuous jet into regular slugs of water. The objective of the simulation was to verify whether dynamic meshes can be used to simulate above mentioned problem and satisfactory agreement of the simulation and reality can be obtained.
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