Computational Fluid Dynamics

The ØDS Machinery Dynamics Group has developed a strong expertise within the field of Computational Fluid Dynamics (CFD). This strategic move positions the ØDS Machinery Dynamics Group as one of the most respected independent consulting companies.

CFD is a novel and unique way to predict fluid dynamic phenomena accurately.

The ØDS Machinery Dynamics Group now offers to assist you to master this complex field.

Our experience with turbomachinery and rotor dynamics is
especially strong.

• Compressors and Pumps
• Turbines and Propellers
• Offshore Structures
• Marine Structures
• Wind Turbines
• Piping
• Trains, Ships and other Transportation Vehicles
• Rotor dynamic Coefficients
• Transient Rotor-Stator Interaction
• Leakage Flow
• Swirl Brake Design
• Stall and Cavitation
• Secondary Flow
• Efficiency and Performance
• Fluid-Structure Interaction
• External Aerodynamics
• Aeroacoustic Noise

Computationl Fluid Dynamics

Background and Approach

Computational Fluid Dynamics (CFD) is based on the simple concepts of linearisation, discretisation and interpolation. In a CFD analysis, the flow domain is partitioned into small volumes that all have to obey a number of conservation equations, such as the nonlinear partial differential Navier-Stokes equations.

Due to the complexity of CFD modelling, the approach was first introduced into research-intensive areas, such as external aircraft aerodynamics and internal gasturbine aerodynamics. In recent years, the approach has matured sufficiently to be used in industrial applications.

Reliable CFD results require specialist expertise and the ØDS Machinery Dynamics Group has spent several years on research and development to reach this level. The international research institutions von Karman Institute for Fluid Dynamics and the Texas A&M University Turbomachinery Laboratory have been extensively involved in the ØDS research project, which has resulted in many journal and conference papers.

Careful verification of the CFD results is important. To us this means:

• Verification of model assumptions
  
• Assuring mesh quality
  
• Comparison with physical tests

Turbomachinery
CFD can be used for several types of
analyses in turbomachinery:

• Rotor dynamic coefficients
• Steady and unsteady flow fields
• Leakage flow
• Stage and machine performance
• Stall phenomena
• Cavitation
  

For all these types of analyses, CFD can be applied both in the design and troubleshooting phase.

In many cases, CFD can replace expensive testing of components. CFD can predict phenomena that are very difficult, if not impossible, to measure.

Additional Applications
At ØDS, CFD has been successfully applied to train and marine applications. For instance, the transient aerodynamics around a train entering a tunnel and the aerodynamics around the electrical equipment (rheostats) on the top of trains have been studied. The main scope of these investigations has been the flow induced acoustic noise.



For marine applications unsteady pressure forces and cavitation from hull-propeller interaction are predicted by using the inhouse developed program “ProPulse” based on the boundary element method.

Tools
ØDS uses state-of-the-art tools for CFD analysis, including CFX-TASCflow, CFX Turbogrid and CFX-Build.

Furthermore, in-house CFD perturbation and grid codes for rotor dynamic analysis have been developed. These tools enable ØDS to make CFD based prediction of rotor dynamic coefficients, and position ØDS as a world-leading expert within this area.

Assignments requiring fluid dynamic measurements using techniques such as Laser Doppler Velocimetry (LDV) can also be performed. The ØDS Machinery Dynamics Group is well experienced in these techniques, and advanced experimental equipment can be made available.

Experience
ØDS primarily uses CFD analysis for design verification, troubleshooting and research. It is our experience that many flow, vibration or noise problems can be avoided or resolved with the correct use of CFD analysis and correlation with measurements when possible.

However, it should be emphasized that CFD analysis is one of many tools. At ØDS, we always try to select the best tool for a given task.