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Problem with the centrifugal pump is calculated for the occurrence of cavitation |
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February 2, 2022, 09:55 |
Problem with the centrifugal pump is calculated for the occurrence of cavitation
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#1 |
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Sergey
Join Date: Jan 2018
Posts: 18
Rep Power: 8 |
I ask for help with the question below questions in 3 languages: English, German and Russian.
Grateful for any help. The centrifugal pump is calculated for the occurrence of cavitation in the impeller. The calculation consists of 2 stages: Stage #1 Stationary calculation in a two-phase medium. We use the Rayleigh–Plesset model. At the beginning of the liquid -1, Gas - 0, set the pressure of saturated vapors, etc. The calculation proceeds normally, an acceptable result is obtained. Cavitation occurs where needed. Stage #2 Non-stationary calculation. To start the non-stationary calculation, the previously obtained stationary growth is used. The problem is that after about 20-30 iterations (20 minutes of calculation on a 32-core processor) an error occurs - OWERFLOW. What is the possible reason for the error? How to eliminate it? What method of receipt calculation in a two-phase medium is acceptable for pumps? ---------------- Die Kreiselpumpe wird auf das Auftreten von Kavitation im Laufrad berechnet. Die Berechnung besteht aus 2 Stufen: Stufe 1 Stationäre Berechnung in einem zweiphasigen Medium. Wir verwenden das Rayleigh-Plesset-Modell. Stellen Sie zu Beginn der Flüssigkeit - 1, Gas - 0 den Druck der gesättigten Dämpfe usw. ein. Die Berechnung läuft normal ab, es wird ein akzeptables Ergebnis erhalten. Wo es nötig ist, tritt Kavitation auf. Stufe 2 Instationäre Berechnung. Um die instationäre Berechnung zu starten, wird die zuvor empfangene stationäre Berechnung verwendet. Das Problem ist, dass nach etwa 20-30 Iterationen (20 Minuten Berechnung auf einem 32-Kern-Prozessor) ein Fehler auftritt - OWERFLOW. Was ist die mögliche Ursache für den Fehler? Wie kann man es beseitigen? Welche Methode der Zugangsberechnung in einem zweiphasigen Medium ist für Pumpen akzeptabel? --------------- Рассчитывается центробежный насос на возникновение кавитации в рабочем колесе. Расчёт состоит из 2-х этапов: Этап №1 Стационарный расчет в двухфазной среде. Используем модель Rayleigh–Plesset. В начале жидкости -1, Газ - 0, задаем давление насыщенных паров и т.д. Расчет идет нормально, получается приемлемый результат. Кавитация возникает там где нужно. Этап №2 Нестационарный расчет. Для запуска нестационарного расчета используется ранее полученный стационарный растёт. Проблема – примерно через 20-30 итераций (20 мин. расчета на 32 ядерном процессоре) возникает ошибка – OWERFLOW. В чем возможна причина ошибки ? Как ее устранить? Какая методика проведения квитанционного расчёта в двухфазной среде приемлема для насосов? |
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February 2, 2022, 17:53 |
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#2 |
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Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,841
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Convergence on cavitation models can be challenging. I do not know of any problems specific to transient cavitation models.
All I can suggest is the normal stuff to improve convergence: * Double precision numerics * Better mesh quality * Smaller time steps * Tighter convergence criteria
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Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum. |
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