Andrzej Szmuk Posted November 29, 2021 Report Share Posted November 29, 2021 Good day. I have a problem with "piston effect" in simulation. The train runs in th e tunnel at a speed of 100 km / h every 4 minutes. The results for air velocity and air volume seem correct. I have a problem with the pressures. They are very small. Please explain how the "piston effect" is calculated? am I making a mistake somewhere? Enclosed are photos with the results ... I am asking for a quick reply. Sincerely, Szmuk Andrzej Quote Link to comment Share on other sites More sharing options...
Martin Griffith Posted November 30, 2021 Report Share Posted November 30, 2021 Hi Andrzej, My first comment would be that you are plotting the variation of airflow and velocity over time, but the variation of pressure over length, which would be for only a snapshot in time. You would need to plot the pressure over time at a single point, as you have for the airflow and the velocity. Another thing to be careful of when using the piston effect to simulate an intermittent effect like a train is that the air simulation of the Dynamic Simulation is a series of steady state simulations. This means there is effectively an instant acceleration of the flow; therefore, the inertia of the air is not taken into account. This means that the peak airspeeds during the dynamic simulation are possibly overestimated. The extra pressure from the piston effect is calculated by correcting the drag force on the train (a function of drag coefficient, frontal area and relative velocity) into a pressure across the cross-section of the tunnel. Another thing to be careful of for trains is they often have very high blockage ratios; the effect of high blockage ratios on the piston effect is something that we have not yet fully considered and are researching more. Interested to see how you go using the feature. Quote Link to comment Share on other sites More sharing options...
Andrzej Szmuk Posted December 7, 2021 Author Report Share Posted December 7, 2021 (edited) Good day. I check the "piston effect" in 1000 ways ;-) The program lacks: 1. During dynamic simulation, it does not show the pressures related to the piston effect. 2. Inability to generate charts from "DYNAMIC MONITOR" 3. Is it possible to graphically show moving vehicles better? 4. "Pressure Total Relative" does not change in dynamic simulation. And it is very important. Because you could read the pressures in front of and behind the vehicle. Please, analyze the possibility of introducing the above comments. I believe this will contribute to the development of the program. ;-) Sincerely, Szmuk Andrzej Edited December 7, 2021 by Andrzej Szmuk Quote Link to comment Share on other sites More sharing options...
Andrzej Szmuk Posted December 7, 2021 Author Report Share Posted December 7, 2021 On 11/29/2021 at 11:18 PM, Andrzej Szmuk said: Good day. I have a problem with "piston effect" in simulation. The train runs in th e tunnel at a speed of 100 km / h every 4 minutes. The results for air velocity and air volume seem correct. I have a problem with the pressures. They are very small. Please explain how the "piston effect" is calculated? am I making a mistake somewhere? Enclosed are photos with the results ... I am asking for a quick reply. Sincerely, Szmuk Andrzej Quote Link to comment Share on other sites More sharing options...
Andrzej Szmuk Posted December 7, 2021 Author Report Share Posted December 7, 2021 I forgot to add that I have version 5.4.2.0 and I'm not sure that these problems have been fixed in newer versions ... Quote Link to comment Share on other sites More sharing options...
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