Using ANSYS Fluent on ARCHIE-WeSt

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This article provides a summary of work carried out as part of the EPSRC funded “SME Engagement Springboard for Archie-West (EP/L019574/1)“. The aim of this project was to lower the barriers to the adoption of High Performance Computing in Industry, with a particular focus on the use of Ansys by SME’s. The full manual, containing instructions on how to work through the examples below, along with input files, is available here. A zip file containing input data and job-scripts is available here.

Air-Water Mixing Tank - Volume fraction of Air

Volume Fraction of Air in an air-water mixing tank

Simulation of complex fluid systems requires the system to be divided into a large number of discrete elements. Calculating how these discrete elements interact with each other given a set of boundary conditions can be quite computationally and memory intensive. Due to the relatively weak power of a regular desktop machine and the restrictive and expensive nature of ANSYS licenses, this can mean some fluid dynamics simulations can take days to complete. However, using a High Performance Computing (HPC) system such as ARCHIE-WeSt allows for effective parallelisation of complex tasks and calculations, drastically reducing the time required to complete simulations of complex fluid systems. When using ANSYS Fluent on ARCHIE-WeSt, it is possible for users to run multiple simulations on multiple cores allowing for the effective optimization of complex geometries and process conditions. Users can also take advantage of upto 32 cores for a single simulation for the most substantial improvement in simulation time. For further details on licensing, contact your departmental IT support or support [at] archie-west [dot] ac [dot] uk.

 

 

Full Shell and Tube Heat Exchanger - Performance Chart

Performance chart for the full Shell and Tube Heat Exchanger example

Performance

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To demonstrate the improvements granted by using ARCHIE-WeSt, four different cases were prepared and then simulated using a journal file on 1 core of a Dual Intel® Xeon® E5-2620 processor on a local desktop machine and then on 4, 8 and 12 cores of a Dual Intel® Xeon® X5650 Processor node on ARCHIE-WeSt. The improvement in time taken to complete the simulation was represented as the speed of the simulation relative to the single core simulation, which was calculated as the time taken for the single core simulation divided by the time taken for the multi-core simulation. The level of improvement varies from case to case but overall the speed of the simulation scales up well with the number of cores used.

Example Cases

 

Example 1: Full Shell and Tube Heat Exchanger

This example illustrates the simulation of the flow-field of a water-water shell and tube heat exchanger where the shell-side fluid passes through the shell once moving around 13 baffles and the tube-side fluid passes once across the shell through 22 tubes. The exchanger operates in counter-flow and both the shell-side and tube-side fluids enter the heat exchanger at 0.1 m/s.

Full Shell and Tube Heat Exchanger - Geometry

Geometry of a full shell and tube heat exchanger

Full Shell and Tube Heat Exchanger - Velocity Contours along the symmetry plane

Velocity Contours along a cross-section of a Full Shell and Tube Heat Exchanger

The movie shows the time evolution of the velocity vector field. The movie is best viewed full-screen and at full HD (click on the settings ‘cog-wheel’ icon to access HD options).

 

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Example 2: Partial Shell and Tube Heat Exchanger

In this example, the thermal profile of a partial water-water shell and tube heat exchanger is simulated over time. Like the previous example, both fluids only make one shell pass and the exchanger operates in counter-flow. However, this example uses a shorter shell with only 6 baffles and no tube-side inlets or outlets. The shell side fluid enters at 288.15 K, the tube-side fluid enters at 363.15 K, the heat exchanger is made from copper and is well-insulated from the environment. The fluids enter at 1 m/s.
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Partial Shell and Tube Heat Exchanger - Isometric Geometry View

Isometric view of the geometry of a Partial Shell and Tube Heat Exchanger


The movie shows the time evolution of the thermal contour map. The movie is best viewed full-screen and at full HD (click on the settings ‘cog-wheel’ icon to access HD options).

Example 3: Air-Water Mixing Tank

For this example, water enters a mixing vessel with a head space full of air at 0.4 m/s. The water is then agitated by a simple rushton turbine moving at 100 rpm before leaving the vessel. This is simulated over a period of time to analyse the flow of the air and the water in the vessel.

Air-Water Mixing Tank - Isometric Geometry view

Isometric view of the geometry of a air-water mixing tank

Air-Water Mixing Tank - Velocity vectors

Velocity vectors of a air-water mixing tank

 

Example 4: Biodiesel CSTR

This example simulates the production of biodiesel in a CSTR. First, the vegetable oil (taken to be pure Triolein and methanol reactants have their flow field in the vessel developed before the reaction to produce Methyl Oleate and Glycerol is simulated over a period of time.

 

Biodiesel CSTR - Geometry

Geometry of a Biodiesel CSTR

Biodiesel CSTR - Methyl Oleate mass fraction contours

Contours of the mass fraction of Methyl Oleate (i.e Biodiesel) in a Biodiesel CSTR

 
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