Examples of system for generating vortex cavity are disclosed. The system comprises a vessel into which a fluid is injected through one or more inlet ports and a fluid circulating system configured to circulate the fluid through the vessel such that the fluid is removed from the vessel through an outlet port and is returned back into the vessel through the one and more inlet ports. A first spinner is mounted at one wall of the vessel while a second spinner is mounted at the opposite wall of the vessel such that the second spinner is at some distance away from the first spinner and it faces the first spinner. When the fluid circulating system starts circulating the fluid within the vessel a vortex cavity is formed that extends between the first and the second spinners so that one end of the vortex cavity sits on the first spinner while the opposite end of the vortex cavity sits on the second spinner.