下载掌阅APP，畅读海量书库
立即打开
When we study the laws of material movement and various natural phenomena, conduct scien tific research or solve technical engineering problems, some special situations including largere search objects, inappropriate changing processes or dangerous environments are often encountered.As a result, it is difficult to perform direct research and on-site measurement on these objects.Therefore, based on the similarity theory, people can create a similar model to imitate the actual situation in laboratories, which may reproduce, delay or accelerate the corresponding physical phenomenon or process of the object, then the research and measurement on the object can be realised.This method is called the simulation. Usually, simulation can be divided into physical simulation and mathematical simulation.
The physical simulation refers to the simulation that the physical essence of the artificially manufactured model is the same with that of the actual research object. The physical simulation mustmeet the following conditions. First, the geometric size of the model is reduced or enlarged in proportion to the geometric size of the original content, in other words, the model and the original content are completely similar in shape. This is called the geometric similarity condition. Second, the model and the original content are required to comply with the same physical laws. Only under this condition can the model be used to test and research within the scope of physical laws instead of the original content, which is physical similarity.
For example, in order to develop the dynamic characteristics of a new type of aircraft flying at high speed in the air, a model similar to the actual aircraft geometry needs to be created, and then placed in a wind tunnel (high-speed airflow device) to create a similar researching environment to that of the original aircraft in the air. Through the force test of the aircraft model, we can easily obtain reliable data in a short time at a small cost.
The mathematical simulation method refers to the simulation that two physical phenomena or processes are completely different in physical essence but have the same mathematical forms. Mathematical simulation is also called after analogy. It satisfies neither geometric similarity nor physical similarity conditions. The original content as well as the built model have nothing in common in form or essence of physical laws, but they do follow the same mathematical forms.
For example, the electrostatic field and the steady current field are originally two different fields, but the physical laws followed by these two fields have the same mathematical forms. Therefore, the steady current field can be used to simulate the electrostatic field which is hard to measure directly. And the potential distribution in the constant current field is used to simulate the potential distribution of the electrostatic field.
If the above two simulation methods are well used, they will certainly be much more effective.Simulation is a simple and easy testing method, which is widely used in modern scientific research and engineering design. For example, in the development of space science and technology, simulation experiments are usually carried out to obtain reliable and necessary experimental data. Simulation is very useful in hydropower construction, underground mineral exploration, and electric vacuum device design.
It should be pointed out that the computer simulation which uses the computer to carry out experimental aided design and simulation experiments has become a brand-new simulation method.The extensive application of computers in the natural science fields has brought great revolution for these researches on physical experiments. Computers can be used to process data in physics experiments, control the experimental process through analog-to-digital and digital-to-analog conversion,demonstrate physical phenomena and physical processes through computer simulations, conduct computer-aided experiments or corresponding aided design and many others. Computational physics, which is currently believed to be the same important as experimental physics and theoretical physics has become the third pillar of physics. Especially, some methods in the computational physics are identical with that in the computer simulation.