Non-steady flow simulating method for pipe network system
A non-constant flow, analog method technology, applied in instruments, computing, electrical and digital data processing, etc., can solve the problem of low simulation accuracy, and achieve the effect of simple coding, fast calculation speed, and simplified calculation complexity
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[0131] Example 1
[0132] In the pipeline system, the implicit difference method is used to solve non-prismatic pipes, and the explicit difference method is used to solve other pipelines.
[0133] The draft tube is a non-prismatic pipeline whose pressure value is an important adjustment parameter during the transition process of a hydropower station. The draft tube is a variable cross-section flow passage. Excessive negative pressure in the draft tube of a hydropower station will cause the steel lining to instability , Water column separation and other unfavorable phenomena, too low pressure may also lead to the release of gas in the water body, and the resulting shock pressure causes cavitation and vibration of the turbine runner. Turbine flow and torque characteristics are generally determined by the comprehensive characteristic curves of the runner model under stable conditions. These characteristic curves do not include the influence of the inertia of the water flow under the u...
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[0134] Example 2
[0135] In the pipeline system, the surge tank is solved by the implicit difference method, and other pipelines are solved by the explicit difference method.
[0136] Using the method of the present invention to solve the surge tank surge mainly includes two steps: the first step is to use the explicit format difference method and the implicit format difference method to solve jointly; the second step is to use the implicit format dynamic grid to track the free water surface of the surge tank.
[0137] see Picture 10 The surge chamber and pipeline shown, the upstream and downstream pipelines of the surge chamber are solved by the characteristic line method, and the surge chamber is solved after being discretized by the Preissmann four-point implicit scheme.
[0138] The surge chamber is divided into n sections, and the last section n is the free water surface. When the grid is determined, the head H n It is known that the supplementary equation for the first section...
Example Embodiment
[0156] Example 3
[0157] In the pipeline system, the implicit difference method is used to solve the full-flow pipeline, and the explicit difference method is used to solve the sub-flow pipeline.
[0158] The basic equation of open channel unsteady flow can be solved using explicit and implicit difference schemes. The explicit difference scheme is mainly the characteristic line method. One of the solutions is to satisfy the Courant condition, the time step is limited, and the numerical stability is difficult to guarantee. ; Second, interpolation is needed, and interpolation errors are difficult to avoid, especially when the transient process is fierce. Use this calculation method with special care, and the errors sometimes overwhelm the actual results. Therefore, the display difference format is generally less used in the calculation of full flow.
[0159] for Picture 12 As shown in the hydropower station with diversion tunnel combined with tailrace tunnel or tailrace tunnel with ...
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