This paper experimentally investigates the effect of two hole positions (post-rib and pre-rib) on film outflow characteristics under different rotation numbers (Ro = 0, +/- 0.4, +/- 0.8) and blowing ratios (M = 0.5, 1.0) by time-resolved particle image velocimetry. The results indicate that at M = 1.0, both hole positions maintain normal film outflow. At M = 0.5, mainstream backflow into the internal cooling channel is observed for the first time under rotating conditions, which is alleviated with increasing Ro, especially under counterclockwise rotation. The post-rib configuration promotes coolant entry into the film hole, whereas the pre-rib configuration, located within the recirculation zone behind the rib, significantly hinders outflow and intensifies backward flow. At the same absolute Ro, counterclockwise rotation enhances film outflow more effectively than clockwise rotation, and this enhancement is more pronounced at the lower blowing ratio. Additionally, the coolant jet exhibits spanwise deflection under the combined action of centrifugal force and Coriolis force. Clockwise rotation causes a pronounced rightward deflection, while counterclockwise rotation results in minimal lateral shift due to force cancellation. The jet velocity and normal range are substantially larger for the post-rib than for the pre-rib.
The author recaps software development over the course of his career and how George Sheldrick inspired and improved this. He concludes that software development is more accepted at present as a role for research scientists, but that more consideration is needed for long-scale project development.
The internal pressure induced by a dominant wall opening threatens the safety of claddings in the building envelope. This paper investigates the influence factors of internal pressure by conducting the wind tunnel test. The combination of proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) methods is applied to analyze the mechanism of internal pressure attenuation and amplification. POD-DMD methods can inhibit unreal modes with high frequencies effectively and extract the physical modes, corresponding to the mean pressure and Helmholtz resonance. The most dangerous internal pressure is induced by the windward and sideward openings. The high-order DMD mode at the Helmholtz frequency reveals the dynamic of air flow through the opening. The mode energy in the internal space is strengthened by a smaller internal volume, a larger opening area, a thick opening, and a lower wind velocity. Current wind loading codes may be unconservative to evaluate the internal pressure with a dominant wall opening in the testing flat-roofed building when the wall opening ratio (the opening area/the total wall area) is in the range of 1%-3.1%. The non-dimensional empirical fitting formulas based on the covariance integration principle are proposed to estimate the internal pressure of the flat-roofed and cylindrical-roofed buildings. The estimating errors are within 10% of testing values, which is much lower than that estimated by the previous approach.
Non-condensable gas-assisted cyclic steam stimulation (NCG-CSS) elevates reservoir pressure during heavy oil recovery; however, the resultant thermal front expansion triggers complex multiphase inter-well interference with adjacent cyclic steam stimulation (CSS) patterns. The fluid mechanics and thermodynamic mechanisms governing this interference remain poorly understood. Integrating multi-stage experiments, this study elucidates the spatiotemporal evolution of temperature profiles and multiphase flow behavior during NCG-CSS and CSS interaction. We formulate a zonal characterization model for NCG and steam flow that, coupled with a stepwise quasi-steady-state approach, enables precise prediction of interference onset and fluid recovery. Results reveal interference evolves through two distinct thermodynamic phases: the X-Y and Y stages. Initially (X-Y stage), the thermal front expands along the inter-well axis, confined near preexisting heated zones. Subsequently (Y stage), longitudinal deflection of the temperature distribution penetrates orthogonally into cold oil zones. While aggregate cumulative production is enhanced by 6.3% and 16.1% during these respective stages, energy efficiency degrades, with the oil-steam ratio dropping by 15.3% and 30%. The interference is governed by thermal front expansion: steam supplies the dominant heat input, whereas NCG redistributes pressure and promotes steam and hot water flow. Excessive injection enlarges the radius disparity between adjacent thermal fronts, weakening interference-area expansion. Thermal redistribution between wells affects production performance, a mechanism that becomes increasingly pronounced as interference intensity rises. By extending wellbore-constrained flow theory from the vertical (X-Z) to the horizontal (X-Y) plane, this study provides a holistic multiphase framework for multi-well interaction in porous media.
Minimizing the excitation force of a composite pump-jet propulsor is critical for suppressing propulsion-system noise and enhancing the acoustic stealth of the platform. When the fluid-structure interaction (FSI) deformation of the composite rotor interacts with variations in structural parameters, the resulting excitation force becomes highly nonlinear. To address this issue, a steady-state FSI algorithm is employed for the pre-deformation design of the composite rotor, and a transient FSI algorithm is adopted to investigate the influence of three parameters-stator angle, duct length, and tip clearance-on the rotor excitation force. The results show that: (1) the stator angle directly affects the rotor excitation force by altering the inflow angle of attack. A larger stator angle increases the time-averaged rotor thrust, which in turn amplifies the excitation force amplitude at the stator blade-passing frequency. (2) The duct length indirectly influences the rotor excitation force by changing the internal flow rate and consequently the wake fraction of the inflow field. Variations in duct length introduce two competing mechanisms: increasing the duct length suppresses radial flow diffusion in the mid-to-low radius region, thereby raising the local flow rate; conversely, the accompanying increase in wall friction expands the turbulent wake region at higher radii, reducing the local flow rate. The interplay between these effects produces a synchronous V-shaped variation in flow rate, pressure distribution, wake fraction, and excitation force amplitude as the duct length changes. (3) The tip clearance affects the rotor excitation force by modifying the turbulence characteristics within the clearance. Changes in clearance height generate two competing mechanisms: a larger clearance intensifies turbulent mixing between the tip-leakage flow and the mainstream, which decreases the time-averaged thrust and thereby reduces the excitation force amplitude; however, it also enhances the phase coherence of excitation forces across different radial sections, which amplifies the overall excitation force amplitude. The net excitation-force response is determined by the competition between these two effects. (4) Replacing the metal rotor with a composite rotor while retaining the baseline geometry yields superior excitation-force characteristics without altering the stator angle, duct length, or tip clearance, and maintains comparable propulsive efficiency. For the specific pump-jet geometry and operating condition investigated in this work, the present study elucidates the mechanisms by which composite rotors suppress excitation forces and provides a theoretical foundation for the engineering design of low-noise composite pump-jet propulsors.
