scholarly journals Computational fluid dynamic modelling of supersonic ejectors: comparison between 2D and 3D modelling

2021 ◽  
Vol 2116 (1) ◽  
pp. 012091
Author(s):  
Giorgio Besagni ◽  
Lorenzo Croci ◽  
Nicolò Cristiani ◽  
Fabio Inzoli ◽  
Gaël Raymond Guédon
Keyword(s):  
Numerical Study ◽  
Fluid Dynamic ◽  
A Priori ◽  
Dynamic Modelling ◽  
Global Scale ◽  
Entrainment Ratio ◽  
Local Flow ◽  
Supersonic Ejector ◽  
Precise Knowledge ◽  
Flow Phenomena

Abstract It is known that the global performances of ejector-based systems (viz., at the “global-scale”) depend on the local flow properties within the ejector (viz., at the “local-scale”). For this reason, reliable computational fluid-dynamics (CFD) approaches, to obtain a precise and an a-priori knowledge of the local flow phenomena, are of fundamental importance to support the deployment of innovative ejector-based systems. This communication contributes to the existing discussion by presenting a numerical study of the turbulent compressible flow in a supersonic ejector. In particular, this communication focuses on a precise knowledge gap: the comparison between 2D and 3D modelling approaches as well as density-based and pressure-based solvers. The different approaches have been compared and validated against literature data consisting in entrainment ratio and wall static pressure measurements. In conclusion, this paper is intended to provide guidelines for researchers dealing with the numerical simulation of ejectors.

Towards a self-consistent thermodynamic magmatic model for conduit transport processes

2020 ◽  
Author(s):  
Jost von der Lieth ◽  
Matthias Hort
Keyword(s):  
Numerical Study ◽  
Numerical Models ◽  
Fluid Dynamic ◽  
Dynamic Modelling ◽  
Explosive Volcanism ◽  
Transport Processes ◽  
The Other ◽  
Full Potential ◽  
Holistic View ◽  
Self Consistent

<p>The geodynamical side of explosive volcanic eruption modelling on the one hand, as well as the petrological one on the other, have reached a high degree of sophistication and maturity independently from each other over the years. Unfortunately, adherents of one discipline often only utilize the other’s tools in a simplified and makeshift way, obscuring the full potential of their synergies. Over the past decade efforts have been made to re-integrate both approaches to the issue into a more holistic view on the sub-surface processes leading to and concurrent with explosive volcanism.<br>One of the difficulties encountered in that effort are conceptual and technical incompatibilities between thermo- and fluid-dynamic modelling toolboxes. While the tools perform well individually, they are often not suitable to work in combination in highly complex numerical models, due to interface problems impeding performance.<br>For an ongoing numerical study on transport processes within a volcanic conduit, it has been deemed necessary to re-implement an established thermodynamic model based on Holland and Powell (2011, and follow-ups) in order to a) attain the required computing performance and b) to gain sufficient petrological insight (starting from a geophysical point of view) to be able to make apt use of the tool then at hand.<br>The path to the intermediate goal of deriving the thermodynamic and transport properties (e.g. density, viscosity, heat capacity and conductivity) in a <em>self-consistent and stable</em> manner suitable for further use in a numerical fluid-dynamics model is illustrated here. The focus is on problems encountered with the petrological modelling, and on the subsequent derivation of the above properties, that are not directly available from the former results. The methods presented are general and applicable to various settings regarding volcanic chemistry and transport processes, however, they will be demonstrated on low-viscosity open-conduit systems typical for strombolian activity.</p>

Numerical Study on the Flow Structure of a Steam-Jet Vacuum Pump at Different Throat Length

2012 ◽  
Vol 542-543 ◽  
pp. 1053-1056
Author(s):  
Xiao Chun Dai
Keyword(s):  
Flow Structure ◽  
Software Package ◽  
Numerical Study ◽  
Simulation Software ◽  
Vacuum Pump ◽  
Back Pressure ◽  
Jet Pump ◽  
Flow Process ◽  
Entrainment Ratio ◽  
Flow Phenomena

The aim of the study is to reveal the complication of the flow process of a steam-jet by using the simulation software package (FLUENT). The paper is able to analyze the flow phenomena inside the steam-jet when its throat length was varied. It is found that the entrainment ratio remains unchanged when the throat length is varied. It is also found that the shocking position moved closer to the exit of the vacuum pump and the critical back pressure of the steam-jet pump increased with the elongation of the throat.

Numerical Study of Off-Design Centrifugal Compressor Operation and Flow Phenomena Preceding Surge

2018 ◽  
Author(s):  
Grzegorz Liśkiewicz ◽  
Krzysztof Sobczak ◽  
Matthew Stickland ◽  
Władysław Kryłłowicz
Keyword(s):  
Experimental Data ◽  
Centrifugal Compressor ◽  
Numerical Study ◽  
Numerical Test ◽  
Sudden Onset ◽  
Rotating Stall ◽  
Flow Structures ◽  
Local Flow ◽  
Low Speed ◽  
Flow Phenomena

The paper outlines the results of a numerical analysis of a low-speed centrifugal compressor operating at design and off-design conditions. This included the analysis of surge predecessors. Surge is known to be a reason for the severe damage of compressing units and systems working with them. This phenomenon is also known to have a very quick and sudden onset. Therefore, it is important to understand the nature of flow structures that appear locally prior to the surge onset. It is generally believed that these could include: impeller rotating stall (abrupt or progressive), diffuser rotating stall, and inlet or outlet recirculation. This classification is, however, not sharp and observed flows could represent only selected features of the different phenomena. It is also not clear which structure is most likely to appear in a given system. The paper presents an exhaustive examination of flow structures observed in the case of a low-speed centrifugal compressor. Transient numerical simulations were conducted for both design and off-design conditions. The results were related to the experimental data presented in another paper. The numerical test domain consisted of blower, volute, inlet nozzle and elements of inlet and outlet channels assuring no influence of the boundary conditions on the local flow fluctuations. The analysis of the results included many factors such as: flow in the volute, flow in the impeller, flow in the diffuser and stagnation zones. The most significant flow structures appearing at pre-surge were identified as the inlet recirculation and the phenomenon representing some features of the rotating stall. The simulation, confirmed by experimental data, allowed for a better understanding of pre-surge flow structures in the case of a low-speed compressor, which is very important for the identification of early surge indicators.

scholarly journals Refrigerant selection for ejector refrigeration systems: a multiscale evaluation

2020 ◽  
Vol 197 ◽  
pp. 10011
Author(s):  
Giorgio Besagni ◽  
Lorenzo Croci ◽  
Nicolò Cristiani ◽  
Gaël Raymond Guédon ◽  
Fabio Inzoli
Keyword(s):  
Fluid Dynamic ◽  
Lumped Parameter Model ◽  
Local Flow ◽  
Multi Scale ◽  
Lumped Parameter ◽  
Flow Phenomena ◽  
Phase Out ◽  
Scale Challenges ◽  
Dynamic Phenomena ◽  
Selection Of

The selection of refrigerants for ejector refrigeration systems, within the broader discussion concerning refrigerant phase-out, is a cutting-edge and challenging research topic, owing to the multi-scale challenges in ejector performance. Indeed, it is known that the performances of ejector refrigeration systems depend on the local flow phenomena. For this reason, a precise selection of the refrigerant relies on the understanding of the fluid dynamic phenomena at the “componentscale”, and integrate such information within the so-called “system-scale”. This paper contributes to the current discussion proposing a screening of refrigerants based on an integrated Computational Fluid Dynamic (CFD) Lumped Parameter Model (LPM) approach. In this approach, ejector performances for the different refrigerant are obtained by a validated CFD approach, whereas the cycle is modelled by a Lumped Parameter Model. For the different refrigerants, the energy performances of the systems are evaluated and the effects of the “component-scale” on the “system-scale” are analysed.

Numerical study of fluid dynamic flow within an internal combustion engine cylinder

2017 ◽  
Author(s):  
Ana Marta Souza ◽  
Antônio César Valadares de Oliveira ◽  
Enrico Temporim Ribeiro ◽  
Francisco Souza ◽  
Marcelo Colombo Chiari
Keyword(s):  
Internal Combustion Engine ◽  
Combustion Engine ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Internal Combustion ◽  
Dynamic Flow ◽  
Engine Cylinder

Un-Shocked High Amplitude Standing Waves in Wave-Shaped Resonators

2012 ◽  
Author(s):  
Dion Savio Antao ◽  
Bakhtier Farouk
Keyword(s):  
Numerical Study ◽  
Fluid Dynamic ◽  
Ambient Pressure ◽  
Standing Waves ◽  
High Amplitude ◽  
Prime Mover ◽  
Non Linear ◽  
Resonator System ◽  
Cylindrical Resonators ◽  
Linear Nature

A numerical study of non-linear, high amplitude standing waves in non-cylindrical circular resonators is reported here. These waves are shock-less and can generate peak acoustic overpressures that can exceed the ambient pressure by three/four times its nominal value. A high fidelity compressible computational fluid dynamic model is used to simulate the phenomena in cylindrical and arbitrarily shaped axisymmetric resonators. A right circular cylinder and frustum of cone are the two geometries studied. The model is validated using past numerical and experimental results of standing waves in cylindrical resonators. The non-linear nature of the harmonic response of the frustum of cone resonator system is investigated for two different working fluids (carbon dioxide and argon) operating at various values of piston amplitude. The high amplitude non-linear oscillations demonstrated can be used as a prime mover in a variety of applications including thermoacoustic cryocooling.

Computational Fluid Dynamic Applications for Jet Propulsion System Integration

1991 ◽  
Vol 113 (1) ◽  
pp. 40-50 ◽  
Author(s):  
R. H. Tindell
Keyword(s):  
System Integration ◽  
Fluid Dynamic ◽  
Low Cost ◽  
Separated Flow ◽  
Propulsion System ◽  
Navier Stokes ◽  
Aerospace Vehicles ◽  
Design Engineers ◽  
Flow Phenomena ◽  
The Impact

The impact of computational fluid dynamics (CFD) methods on the development of advanced aerospace vehicles is growing stronger year by year. Design engineers are now becoming familiar with CFD tools and are developing productive methods and techniques for their applications. This paper presents and discusses applications of CFD methods used at Grumman to design and predict the performance of propulsion system elements such as inlets and nozzles. The paper demonstrates techniques for applying various CFD codes and shows several interesting and unique results. A novel application of a supersonic Euler analysis of an inlet approach flow field, to clarify a wind tunnel-to-flight data conflict, is presented. In another example, calculations and measurements of low-speed inlet performance at angle of attack are compared. This is highlighted by employing a simplistic and low-cost computational model. More complex inlet flow phenomena at high angles of attack, calculated using an approach that combines a panel method with a Navier-Stokes (N-S) code, is also reviewed. The inlet fluid mechanics picture is rounded out by describing an N-S calculation and a comparison with test data of an offset diffuser having massively separated flow on one wall. Finally, the propulsion integration picture is completed by a discussion of the results of nozzle-afterbody calculations, using both a complete aircraft simulation in a N-S code, and a more economical calculation using an equivalent body of revolution technique.

Fluid dynamic modelling of electric arcs for industrial applications

1998 ◽  
Vol 70 (6) ◽  
pp. 1163-1168 ◽  
Author(s):  
C. Delalondre ◽  
Alain Bouvier ◽  
Ange Caruso ◽  
Namane Méchitoua ◽  
O. Simonin ◽  
...  
Keyword(s):  
Fluid Dynamic ◽  
Dynamic Modelling ◽  
Industrial Applications ◽  
Electric Arcs
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