Introduction – reasons for good design:
When we buy a new car, we may have a number of expectations. e.g. We would like the car to be fuel efficient, comfortable in the cabin, be able to ride well in all kinds of roads, provide us a safe ride. When an airline buys an aircraft, they have expectations. e.g. Trouble free operation with minimal down time, integrity of the structure of the airplane, comfort of passengers in the cabin, reliable operation of the engine (from taxi, take off, ascent, cruise, descent and landing). When the government has a power plant commissioned, they would like to ensure that the plant delivers the required power, has the infrastructure to meet environmental emission standards and has good efficiency (conversion of energy into electricity). When an appliance manufacturer designs a washing machine, they would like to ensure that the system ensures good mixing of the water and detergent, proper agitation to remove dirt from the clothes and good ability to remove water from the clothes during the spin cycle.
All these examples show that a good design is needed for efficient functioning of the appliance/airplane/power plant etc
Methods of good design:
There are two principal methods for ensuring a good design:
a) Testing of Prototypes and the Final Product
b) Performing virtual simulations using a computer.
The traditional method of design predominantly involved testing. Testing was considered to be the only fool proof method of ensuring a good design. However testing is expensive, time consuming, sometimes not possible in hazardous environments, and has difficulty to replicate all real-world operating scenarios.
b. Virtual simulations
Computer Simulations (also known as Virtual Simulations or Numerical Simulations) provide an attractive alternative. Instead of performing a physical test in a lab, one can perform a virtual test on a computer. The virtual test of course needs to be validated against physical tests (or experiments) to build confidence in the computer simulation. The cost involved for performing Virtual Simulations (typically computer hardware, software license and a trained engineer) is a lot cheaper than the cost involved for performing a physical test.
With the ever increasing power of computing, virtual simulations have become a cheaper and time efficient alternative to physical testing.
Now, there are two classes of problems. A) Problems that have an analytical solution b) Problems that do not have an analytical solution. The second class of problems involve modelling assumptions, and the results need to be interpreted carefully, keeping in mind the modelling assumptions. For both class of problems mentioned above, companies have been making a conscious shift from Physical Testing towards Virtual Simulations over the last 15 years.
Companies and design:
Most companies rely heavily on computer simulations at a very early stage of the design cycle to select a group of good designs. During the final stages of design, they test the good designs predicted by simulations. On successful confirmation of the designs, the product is released to the market. This approach enables companies to keep costs reasonable and also shorten the design cycle resulting in valuable time savings. In an evolving, demanding and competitive market environment, Virtual Simulations play a very important role.
Types of simulations:
Simulations themselves could either be 1D or 3D. 1D simulations are faster to run and enable system level simulations (e.g. Entire Powertrain of a Vehicle). 3D simulations take longer to run, but can provide three dimensional information about the system being analyzed (e.g. The temperature and pressure at every location within an Internal combustion engine). Companies typically use a combination of 1D and 3D simulation tools during the product design phase.
Both domestic and multi-national automotive manufactures have traditionally used Wind Tunnels for drag reduction of their vehicles. Reducing drag improves the fuel economy of the car. The manufacturers now use computer simulations to simulate both wind tunnel as well as on-road driving conditions. A computer simulation can provide the manufacturer detailed pressure, temperature and flow distribution around the car (to the tune of several million locations). It would be prohibitively expensive to get the same information from a wind tunnel test (since pressure and temperature transducers and data collection systems are expensive). The computed data can be visualized on a computer.
As the expectations from the market keep rising every year, Virtual Simulations are now playing a very important role to help companies to come up with designs meeting customer requirements.
Mani Prithiviraj has a Bachelors in Mechnaical Engineering from BITS, Pilani and a Master’s and Doctorate in Mechanical engineering from Texas A&M University, College Station, USA. He is currently Director of Customer Success at Siemens Industry Software Computational Dynamics India Pvt Ltd, Bengaluru, India. He can be found here.