Abstract: The present invention provides a turbine airfoil for relative movement in an ambient fluid, and a turbine apparatus comprising at least one airfoil. The airfoil comprises a main spar having two hill formations and discharge means operable to discharge evaporative and condensing fluids outwardly into the ambient fluid flowing over the main spar. The first of these hill formations accelerates the flow of the ambient fluid until it reaches the speed of sound. After the first hill formation the Mach number continues to increase and the evaporative fluid is discharged into the ambient causing the air to cool which accelerates the ambient flow further and decreases the pressure. On the second hill formation the lower pressure causes a thrust. As the flow moves relative to the second hill formation the Mach number decreases and then increases as it descends the second region.