The vertically launched underwater vehicle always suffers various hydrodynamic disturbances in its water-emerging process due to the uncertainty of the launch platform motion. Based on the nested sparse grid based stochastic collocation method (NSSCM) and nonintrusive polynomial chaos method, the effect of uncertainty of platform velocity and yaw angle on robustness of vehicle's trajectory and attitude is numerically studied. Results indicate that the uncertainty stemming from platform motion propagates along vehicle's water-emerging process. As the negative horizontal velocity of vehicle gradually changes to positive direction, the uncertainty bar of horizontal velocity presents contracting-expanding mode with an “hourglass” shape while the uncertainty bar of horizontal displacement experiences a “spindle-shaped” one (expanding-contracting-expanding), which is a half cycle later compared with the velocity. The uncertain motion of platform enlarges the uncertainty bar of bottom force via its impact on the gas-leakage process of trail bubble, resulting in the increasing of uncertainty of vertical velocity. Pitching angle (attitude of vehicle) and pitching angular velocity of vehicle persist getting worse driven by the pressure difference between vehicle's front and back sides especially on head part. And their continuous increasing uncertainty bars are formed mainly due to the condition that pressure uncertainty of front side is larger than that on back side, which also leads to the increasing of uncertainty of horizontal force.

Vortex generator jets (VGJs) have been used to suppress the flow separations in bowed compressor cascades at different incidences via numerical calculations. The results show that with momentum injection and streamwise vortex produced by VGJ, the total losses in the bowed blades effectively decrease whereas the static pressure ratios increase. For the positively bowed blade, at $-5°$ incidence, with slight flow separation, the mixing loss caused by VGJ is dominant and the loss increases by 1%; with an incidence ranging from 0° to $+5°$ , the regions of the flow separations all decrease, and the total losses decrease by 2.7 and 5.4%, respectively; with the incidence increasing to $+7°$ , the separation type converts from closed to open, and the loss decreases by 6.8%; when the incidence is $+10°$ , one concentrated shedding vortex disappears, and the loss decreases by 9.27%. For the negatively bowed one, as the incidence increases from $-5°$ to $+7°$ , the flow separations are all effectively suppressed when all the separation types are closed, and the losses decrease by 2.9, 9.1, 17.5, and 19.75%, respectively. When the incidence increases to $+10°$ , however, because of the huge range of flow separation, there is no improvement in the flow field, but the total loss increases by 1.37%.

Pressure-equalizing film is a slice of air film generated through exhausting and attached to the vehicle's exterior with nearly uniform inner pressure. Similar to ventilated cavity in composition, but of interest, here is the weakening of pitching moment and environment disturbance that the film offers, the film's forming speed and covering range upon vehicle determine the improvement effect of vehicle's trajectory stability as it emerges from water. This paper established a numerical approach to investigate the effect of single and double rows of venting holes on the evaluation of air film along vehicle's exterior, at the same time its influence on the trajectory stability of vehicle with three degrees-of-freedom (3DOF) motion is also analyzed. Results indicate that reverse flow forms between row-to-row spacing when exhausting with two rows of holes, which enhances the exhausting process with the film's size enlarged and axial length extended, meanwhile it brings about more complex vortices structure near venting holes compared to the single-row hole case. As for the 3DOF cases, the pressure difference between vehicle's front and back sides is dramatically reduced attributing to the existence of attached air film, consequently the rotation of vehicle is weaken, leaving a better attitude to vehicle after it piercing water surface. Besides, the rapid formation of air film in double-row hole cases is advantage for the timely inhibiting of vehicle's pitching motion compared to the single-row hole cases, and their weaker stagnation high pressure near film's closure region is also good for the reduction of vehicle's lateral load.

Many uncertain factors in the water-emerging process of a vehicle influence the taking effect of the air film around its shoulder in the load reduction and attitude control. Assuming the launch parameters (launch depth, vehicle velocity, and chamber pressure) as sources of uncertainties, the uncertain evolution process of the air film in the water-emerging process of a vehicle is quantified by adopting the nonintrusive polynomial chaos (NIPC) method with the sample space constructed using linearly independent probabilistic collocation points. A sensitivity analysis was conducted for the key performance indicators of the air film to evaluate the contribution of each uncertain launch parameter.