City University London                   School of Engineering and Mathematical Sciences




DOWNLOADS:     DISCO-Demo   VoloView

   Install.Instructions  About DISCO

Short Course and Forum on


City University, London, 7-8 September 2013


Organised prior to the 8th International Conference on Compressors and Their Systems,

City University, London, 9-10 September 2013



IMech Banner Image                                                                                            DISCO1


The University will present the second series of courses on compressor technology with emphasis on screw compressors. This course is dedicated to advanced topics in application of CFD to rotary positive displacement machines for industrial use and research. Topics to be covered include: grid generation for complex geometries, advances in CFD methods, turbulence modelling and validation of CFD performance prediction, Integration with CAD and Industrial applications. It will be delivered by the leading experts in CFD, vendors of CFD codes, academics and industrial users.


The course and forum will take place at the Northampton Square site of City University London prior to the 8th Conference on Compressors and their Systems on Saturday 7th and Sunday 8th September 2013. The course will be delivered in 6 sessions which last 1hr and 30 minutes each. Each block will consist of 1 to 3 lectures. Three blocks will be delivered on each day of the course. The discussion forum will take place at the end of each day in order to address the issues identified during the course.





blebul1a  Objectives

blebul1a  Program

blebul1a  Lecturers

blebul1a  Cost

blebul1a  Express interest to attend & Register

blebul1a  International Conference on Compressors and Their Systems

blebul1a  ConfTool Conference Management System


1)    To provide forum for discussion wide range of issues on CFD in positive displacement machines.

2)    To hear about latest developments in this area from world leading experts

3)    To enable industry and academia meet with CFD and Grid generation vendors

4)    To provide directions for future developments in CFD for positive displacement machines



Saturday, 7th September 9,00-16,00


0900- 0905                    Welcome and Introduction

0905-1045                     Session 1:     General CFD with emphasis on modelling positive displacement machines,
                                                      Including capabilities of StarCCM+

                                                      by Prof Milovan Peric – CD-adapco, Germany


1045-1100                     Coffee break

1100-1230                     Session 2: Grid generation theory and practice

1)      Grid generation and CFD analysis in Screw Compressors
 by Prof Ahmed Kovacevic -  City University London, UK

2)       ANSA and META for pre and post processing of industrial applications
by Dr Dimitris Soliotis - Beta CAE Systems S.A. Greece

1230-1330                     Lunch

1330-15000                    Session 3: Available CFD codes, theory and practice

1)       Use of Ansys CFX and Fluent for analysis of positive displacement machines

by Mike Chudiak -  Ansys, Canada

2)       Application of full 3D and 1D/3D modelling in IC engines

by Dr Vlado Przulj, Ricardo, Nick Tiney – Ricardo, UK

1500-1515                     Coffee break

1515-1600                     Forum 1: CFD and Grid Generation
                                 Moderated by: Prof Ahmed Kovacevic




Sunday, 8th September 9,30-16,45


0930-1100                     Session 4: Application of CFD in other Positive displacement machines

1)      PumpLinx: Virtual Testing of Fluid Pumps, Motors, Compressors, Valves and Systems

by Sam Lawry and Jiang Yu - Simerics, USA

2)      Application of CFD in piston compressors
Prof Cesar J. Deschamps - Federal University of St.Catarina - Brasil 


1100-1115                     Coffee break

1115-1245                     Session 5: Industrial application of CFD in screw compressors

1)      Jack Sauls, Scott Branch -  Trane, Ingersoll Rand, USA

2)      Dr Maria Pascu - Howden Compressors Ltd, Glasgow UK


1245-1400                     Lunch

1400-1530                     Session 6: Future CFD developments in positive displacement compressors

1)      Recent developments in grid generation for Screw Compressors

 by Mr. Sham Rane -  City University London, UK

2)      Opportunities for modelling multiphase flows in positive displacement machines
by Prof. Manolis Gavaises -  City University London, UK

1530-1545                     Coffee

1545-1645                     Forum 2: Future of CFD in positive displacement compressors
                                 Moderated by: Prof Ahmed Kovacevic


1800-2000                     8th International Conference on Compressors and their Systems – Reception and Early Registration





Prof Milovan Peric - CD-adapco, Germany


Positive displacement machines are characterized by moving parts, so the main feature of a CFD method applicable to such machines is the ability to account for various motion patterns. Finite volume methods commonly employed in CFD codes are well suited for moving and deforming boundaries, provided that the space conservation law is properly accounted for in the discretized equations. The main challenge is simulating flows in positive displacement machines lies in accounting for grid motion and its adaptation to moving walls, such that an acceptable grid quality is maintained.

In this lecture, conservation equations for moving/deforming control volumes and their discretization using second-order methods and arbitrary polyhedral control volumes will be presented first. Different possibilities to account for motion of various parts (morphing of grids with a constant topology, re-gridding, sliding of grid blocks attached to moving and fixed parts along curved surfaces, overlapping grids etc.) will be discussed next. Accounting for multiple phases (primarily liquids and gases) and fluid-structure interaction will also be briefly addressed. Some examples of application of STAR-CCM+ software to flows in various positive displacement machines will be shown before trends for future development in this area are introduced (overset grids, automatic local grid adaptation, coupled simulation of flow, heat transfer and deformation of solid structures etc.) and discussed.

Prof. Ahmed Kovacevic - City University London

Prof Kovacevic is Howden Chair Professor of Engineering Design at City University in London. His main research interests are in the integration of computer aided design for positive displacement compressors, Computational Continuum Mechanics in positive displacement machines, research and development of positive displacement compressors with the main focus on screw compressors. As educator he is interested in engineering and mechanical design principles, integration of design methods and tools by use of computers and the international collaborative educational programme.

Computational Fluid Dynamics (CFD) can be readily used for the flow prediction and analysis of screw compressors. Several case studies are presented here to show the scope and applicability of such methods. These include solid-fluid interaction in screw compressors, prediction of flow generated noise in screw machines, cavitation modelling in gear pumps, and flow in multiphase pumps for oil and gas industry. Numerical grids for all these cases were generated by us of an in-house grid generator SCORG(C), while the CFD calculations were performed with a variety of commercially available CFD codes.
In order to validate the accuracy of the CFD calculations, an extended test programme was carried out using Laser Dopler Velocimetry (LDV) to measure the mean and fluctuating velocity distribution in screw compressor flow domains. The measurement results are then compared with the CFD simulations. The results confirm the accuracy of the developed techniques.
Development of new grid generation capabilities for arbitrary rotors creates further opportunities for a broader use of Computational Fluid Dynamics for analysis of variety of screw machine configurations in a range of new applications.

Dr Dimitris Soliotis - Beta CAE Systems S.A. Greece

Dr Dimitris Souliotis works in Customers Service Department responsible for CFD applications. Graduate of the Aristotle University of Thessaloniki (AUTh), Department of Mechanical Engineering. Dimitris holds a Ph.D from AUTh. Dimitris is participating in various International Conferences.


The application of CFD in modern industrial design and analysis has brought up a new field of development across a series of processes and tools. The ability to model complex flow problems on multicomponent assemblies has increased the need for automation in the model pre and post processing. Furthermore the need for constant movement of such models requires high level of automation and robustness in the meshing field.

BETA CAE SYSTEMS S.A. has a long history in the development of CFD pre and post processing multidisciplinary tools that interface with an extended list of software in CAE. It has developed several proprietary meshing tools and algorithms that respond to the needs of a variety of applications and industries in the CFD field. Additionally all the observed phenomena can be automatically processed and realized within the multidisciplinary post processing environment of META.

Within this context we will also emphasize on the tools that will allow the generation of the positive displacement models while interfacing with DISCO software. We will focus on the generation of hybrid mesh in ANSA within an automated process that will produce all the required girds for each time step. The whole process is based on high quality surface representation that ensures the accuracy of the modelling and consequently the accuracy of the simulation. A real time showcase of the grid generation in ANSA will be carried out on a simplified design of a screw compressor coupled with data provided by City University.

Mr Mike ChudiakAnsys,Canada

Mr Chudiak is a Lead Technical Specialist at ANSYS Inc.  Located in Waterloo, Canada, Mike manages a team of engineers in the support and services function.  He has been involved with CFD since 1995, and has been at ANSYS for the past 12 years.

The motion of positive displacement machines adds a unique complication in the accurate modelling of their operation in fluid dynamic calculations. The computational meshes need to dynamically adjust to the movement of the machine parts. Changes to the geometry of the fluid-space can be accounted for in the discretized representation of the volume through various approaches, such as local/global re-meshing, cell layering, mesh deformation, immersed solids, or a combination of multiple techniques. Each method has a cost/benefit balance that needs to be taken into consideration. The best approach for modelling one particular machine may not be optimal (or even possible!) for another.

In this presentation an overview of these techniques and the functionality available in ANSYS CFX and ANSYS Fluent computational fluid dynamic software tools is reviewed. Some example machine applications and solutions will be discussed.

Dr Vlado Przulj and Nick Tiney - Ricardo, UK

Dr Przulj is a Computational Fluid Dynamics professional with more than 20 years of wide experience in mathematical modelling of fluid flows and heat transfer, the algorithm development, associated solution methods and the code development. He is a principal developer in Ricardo Software. Before joining Ricardo he worked for AVL List where he contributed to the development of the AVL FIRE CFD code. His CFD experience encompasses cell-centred, finite-volume pressure based methods applicable to flows at all speeds as well as design of multi-domain and multi-phase object oriented code architecture supporting multi-physics simulations.

VECTIS is a general purpose CFD tool extensively used in engine design where in-cylinder simulations are performed to investigate various phenomena such as fuelling effects, spray injector positioning, piston shape and bowl design and the effects these have on combustion and emissions. These simulations require comprehensive models for fuel sprays and combustion as well as the deployment of moving grid technology.

Considering that a moving grid problem is the generic one, this lecture provides a short theoretical background to moving grids. The emphasis is on the dynamic grids which describe combined deforming and topology modified grids. Topological changes can be introduced by employing either topology modifiers (addition/removal of cell layers, sliding interfaces, local re-meshing) or complete re-meshing. The latter approach is implemented in the VECTIS solver where deforming grid steps using Laplacian smoothing are followed by complete domain re–meshing. Other important elements of in-cylinder simulations such as geometry and grid setup, definition of motion for the valves and piston, strategy and control of in-cylinder events, and resolution of issues associated with opening/closing of the intake and exhaust valves, are also discussed. The results of 1D WAVE code simulations are typically used as initial conditions in the ports and combustion chamber.

Practical demonstration of a typical in-cylinder simulation is also planned. The demonstration will involve preparation of a run strategy, import of the CAD geometry, generation of multiple grid files, definition of moving boundaries and their motion, and presentation of the selected results.

Dr Sam Lawry - Simerics, USAil

Dr. Lowry has served as President of Simerics, Inc. since its founding in 2005. He received an A.B. in Engineering and Applied Physics from Harvard College, an M.S. in Mechanical Engineering from Case Western Reserve University and a Ph.D. in Engineering Sciences from the University of Tennessee Space Institute. Dr. Lowry's prior work experience includes more than 10 years at CFD Research Corporation, concluding as Director of Advanced Technology, and five years as a NASA engineer in the Turbomachinery Branch at the Marshall Space Flight Center..

Computer simulations of pumps and compressors can now serve the same function as hardware testing. These simulations can be done in less time with less cost while providing engineering data of similar quality as experiments. Furthermore, computer modeling can be performed directly by the engineer doing the hardware design, thus providing a tight link between analysis and design optimization. Virtual testing can also be used to analyze problems with existing hardware, either as standalone components or in the context of a system. This presentation focuses on PumpLinx, a Computational Fluid Dynamics (CFD) tool that serves as a virtual test bed. PumpLinx predicts the performance of pumps and compressors in terms of head rise, power, efficiency, cavitation effects, noise, and/or damage. PumpLinx starts with existing designs created in a third party CAD package. Once the geometry is imported, the pump is meshed, modeled, simulated and analyzed, all in a single interface. Various operating conditions and fluid properties can be input to simulate the pump or compressor over a range of operating conditions. The output is similar to what would be measured for a fully instrumented test, with additional flow visualization and integrated quantities. This presentation will provide selected examples of the simulation of compressors and pumps.

Prof Cesar J. Deschamps - Federal University of St.Catarina - Brasil

Prof. Deschamps received his Ph.D. degree in Mechanical Engineering from the University of Manchester, UK, in 1994. He is currently Associate Professor of Mechanical Engineering at the Federal University of Santa Catarina, Brazil, where he has taught courses on Fluid Mechanics, Turbulent Flow and Compressor Thermodynamics. His research interests includes refrigeration compressors, with emphasis on automatic valves and thermal management, as well as turbulent flow and aeroacoustics.

Reciprocating compressors are commonly used in refrigeration systems and can be manufactured economically in a wide range of sizes. The design of a compressor must be assessed by a number of key parameters, such as energy consumption, environmental impact and manufacturing cost. Computational Fluid Dynamics (CFD) allows a reduction in the development of compressors and also the analysis of phenomena that are difficult to assess through experimental investigation. For instance, suction and discharge systems are crucial components of reciprocating compressors, affecting to a great extent their isentropic and volumetric efficiencies, reliability and acoustic noise. Simulation models can be developed to analyze in details pressure pulsation in mufflers, flow irreversibility and valve dynamics. CFD can also be applied in the thermal management of compressors in order to assist the development of technologies to manage thermal energy, its generation, dissipation and recovery. Numerical models are particularly useful for thermal analysis of components and simulation of extensive system interconnections.

Mr Jack Sauls and Mr Scott Branch - Trane, Ingersoll Rand, USA

Jack Sauls, Technology Leader

Scott Branch, Compressor Design Engineer

This brief presentation will focus on examples of how CFD has been used to make specific decisions in the design of refrigeration screw compressors for use in water chillers for comfort cooling applications.
In some cases, designs have been investigated using CFD to explore options and define final design parameters. However, the overhead required for the direct application of CFD analyses for screw compressor design prohibits studies requiring investigation of large numbers of candidate configurations at multiple operating conditions. Such analyses are required though to properly explore the design options and thereby make appropriate design decisions. Such analyses are generally carried out using thermodynamic analyses based on a more complete set of component analyses, but with much simpler models employed, these often based on empirical calibrations.
In recent years, we have sought to use CFD analyses of specific phenomena within the compressor such as leakage and discharge port flows to develop new or improved models for use in the simpler thermodynamic simulations. The process is to carry out limited number of analyses for the specific situation, acquiring information on the effects of geometry and operating conditions then forming this information into a generalized model. In this way, the thermodynamic simulations are “taught” to behave somewhat more like the more complex CFD models.
The presentation will draw on previously published materials as well as some current, unpublished information. We will point out issues encountered in using CFD in this difficult application and will provide an example of a new compressor design.

Dr Maria Pascu - Howden Compressors Ltd, Glasgow UK

Graduated from the Power Engineering Faculty, University "Politehnica" Bucharest in 2005 with a major degree in Nuclear Power Plants

-Obtained her Phd at the Institute of Fluid Mechanics, LSTM Erlangen, Friedrich-Alexander University Nuremberg, Germany in 2009

-Currently employed by Howden Compressors Ltd in the position of R&D engineer

-area of expertise: CFD in rotating machinery; published one manuscript "Axial fan design. Modern layout and design strategy for fan performance optimization" (2009) and over 15 journal and conference papers.

The shape of the suction port in a twin screw compressor is often the subject of experimental investigations and the general belief is that by opening the gas admission through a radial port at the suction will have a positive effect on the compressor performance, as it would improve the chamber filling process by reducing the throttling losses. This hypothesis was tested against a standard WRV163145 compressor and two suction scenarios were analyzed, both experimentally and numerically: one with axial port at the compression chamber entry (the original compressor), the second including the same axial port, as well as a radial port machined-off from the inner casing wall (the modified compressor).
The combined experimental and numerical investigation revealed that there is no improvement to be expected by adding a radial port to the suction arrangement of the investigated screw compressor and furthermore, at higher pressure ratios, a slight deterioration of the compressor performance was observed.
Although the CFD procedure was well validated by the experimental results, there are still a number of issues to be addressed regarding the numerical investigation of screw compressors, especially concerning the meshing techniques. By addressing the flow domain around the tip clearance of the same WRV163145 compressor, some of these issues were highlighted through an extensive grid sensitivity exercise

Mr. Sham Rane - City University London, UK

BE(Mech), MTech(Mech), PhD Student at Centre for Positive Displacement Compressor Technology

Research Interests

• CFD solver and application development

• Customized Grid Generation for Positive Displacement Machines like screw compressors.

Uni-directional and Bi-directional code coupling for multi-physics simulations

The biggest challenge in 3D Transient CFD analysis of Positive Displacement Screw Machines has been the availability of dynamic deforming grids on which the conservation equations need to be solved. A remarkable advancement was achieved in 1999 with the development of SCORG at City University London. This tool is based on techniques of Algebraic Grid generation with Transfinite Interpolation and Boundary Adaptation. SCORG has been successfully used for Twin screw parallel axis machines for a long time.

As the industry sees development of new types of screw machines like Variable Lead, Variable Profile rotors, there is a need to develop grid generation methods suitable for such variations and also for existing machines like Single Screw Compressors.

This lecture will demonstrate how customized grid generation principles and tools can be developed and help CFD development of screw machines. Some examples of recent upgrades of SCORG to generate grids for Variable geometry rotors will be presented.

Prof. Manolis Gavaises - City University London, UK

Prof Gavaises is the director of Energy & Transport Research Centre at City University London. He is a member of the editorial board of Atomisation & Sprays, Applied Mathematics and International Journal of Engine Research. He is on the organisation committee of the IMechE Conference for Fuel Injection Systems for IC Engine, the SIA Conference on Diesel Powertrains and he is the Chairman of the 2013 ILASS-Europe Conference.

CFD simulation of the flow in screw compressors is a complex task: the changing geometry and the very small leakage passages pose difficulties not only to the creating of numerical grids but also on the implementation of methodologies able to resolve the detailed fluid dynamics in such areas. In case of multi-phase flow formation, things become even more complex as there is no experimental information on what type of flows may exist and what models are appropriate for their simulation in such machines. In light of that, this presentation provides a review of relevant multi-phase flow models, their applicability range and their relevance to flow conditions realised in screw compressors. Without having attempted yet to simulate such cases, it is speculated which methodologies sound more appropriate for resolving such cases and what experiments could be designed for their experimental validation.





The fee for the course is £360 for conference delegates and £480 for those attending course only.

The fee includes lecture materials on CD and in the paper form, refreshments, lunches and the evaluation copy of DISCO software with the training lesson.




To express interest in attending the course and to register for the course please see: Compressors Conference pages on our online store

Site prepared and maintained by:

 Prof Ahmed Kovacevic
City University, School of Engineering and Mathematical Sciences, Northampton Square, London, EC1V 0HB, UK
Phone: +44 (0) 20 7040 8780, Fax: +44 (0) 20 7040 8566, E-mail:, Web: