Yingchao Zhang

Automotive thermal-comfort studies commonly focus on interactions between occupants and cabin air, although the seat forms the principal sustained contact interface between an occupant and a vehicle. This study presents a coupled computational fluid dynamics (CFD) framework that simultaneously resolves heat conduction through perforated leather, breathable sponge, heating pads, and foam; porous airflow through the seat; seat heating and ventilation; and convective heat transfer between the occupant and cabin air. Four total seat-heating powers (0, 60, 90, and 120 W) and four ventilation-fan speeds (0, 1500, 3000, and 4500 rpm) were simulated for 900 s. The results show that seat heating primarily alters temperatures in the contact region through conduction, whereas seat ventilation increases local airflow and cooling near the edges of ventilated contact regions. The principal contribution is a reproducible interface between cabin CFD and thermophysiological modeling. The framework generates spatially resolved fields of air temperature, air velocity, skin and contact-surface temperatures, and heat flux that can serve as boundary conditions for physiological models such as the Fiala and Berkeley models and for subsequent experimental validation. Because the present calculations constitute a comparative single-driver study, direct experimental validation, active thermoregulation, subjective thermal sensation, and interactions under full occupancy must be addressed before the framework can provide absolute comfort predictions.

The transient pressure rise in occupants’ ears during vehicle door closure remains a key challenge for cabin comfort, but existing simulation methods often lack accuracy or efficiency. This study develops an integrated experimental–CFD–theoretical framework. A high-fidelity vehicle model was constructed from point cloud data and validated against airtightness and door-closure tests. A theoretical model was derived and calibrated using flow hysteresis and fluctuation attenuation coefficients from CFD results. Uncontrolled leakage was represented by distributed circular holes, and the one-way flow through the pressure relief valve was implemented numerically. The refined CFD model reduced the peak-pressure and amplitude errors from 6.33% and 17.62% to 1.75% and 2.66%, respectively. The calibrated theoretical model achieved 93.94% accuracy in pressure amplitude relative to the CFD results, with much lower computational cost. An optimization strategy combining early valve opening with an auxiliary fan at the relief valve reduced peak pressure, amplitude, and pressure change rate by 25.88%, 22.83%, and 41.23%, respectively. By deeply integrating experiments, simulation, and theory with refined modeling of key physical features, this research overcomes the accuracy and efficiency limitations of traditional methods, offering a systematic solution for cabin comfort optimization and advancing forward-development capabilities in vehicle NVH.

The aerodynamic behavior of a low-drag Ahmed body under yaw conditions was investigated using wind tunnel experiments and numerical simulations. The investigation focused on the evolution of flow structures across various yaw angles. The flow characteristics were systematically analyzed, with particular attention to front separation, lateral pressure distribution, spanwise vortex dynamics, the development of longitudinal vortices, and variations in vertical vortex structures. The displacement of the front saddle point led to the recovery of surface pressure on the front body when the yaw angle exceeded 20°, which was identified as the main contributor to drag reduction under high yaw conditions. Asymmetric front-end separation caused notable disparities in the side-surface flow and wake structures. Despite intensified pressure fluctuations on the windward side, the pressure differential between the two sides serves as a reliable indicator for estimating lateral force or yaw angle. A transition in the near-wake structure from a low-drag to a high-drag mode was observed from the windward to the leeward side. At a yaw angle of 16°, the near-wake fully transformed into a high-drag configuration. These findings enhance the understanding of crosswind aerodynamics in bluff vehicle bodies.

A high-fidelity digital-twin (DT) model of an automotive climate wind tunnel is developed in this study to enable reliable and efficient investigations of vehicle thermal behavior under high-temperature and strong-radiation conditions. The digital twin is established based on a full-scale climate wind tunnel and incorporates detailed representations of airflow organization, thermal boundary conditions, and solar radiation simulation. To validate the accuracy and reliability of the proposed DT model, comprehensive comparisons between numerical simulations and physical wind tunnel experiments are conducted, focusing on airflow temperature characteristics and solar radiation uniformity in accordance with the thermal-field performance evaluation criteria of the real facility. The results demonstrate a high level of consistency between the digital twin and the physical wind tunnel, confirming the capability of the DT model to faithfully reproduce the thermal environment of the experimental facility. Furthermore, the accuracy of the digital twin in predicting vehicle cabin solar-induced heating is assessed through comparative analyses of three scenarios: natural-environment heating experiments, natural-environment numerical simulations, and digital climate wind tunnel simulations. The close agreement among these results verifies the feasibility of conducting vehicle cabin solar-heating studies within the digital climate wind tunnel. Finally, the validated DT model is applied to practical engineering scenarios, including cabin and seat solar-heating simulations as well as ventilation-based cooling under extreme thermal loads. Optimal air-conditioning airflow rates and outlet angles are identified. The results indicate that the proposed digital-twin climate wind tunnel provides an effective and reliable platform for virtual thermal testing, significantly improving research efficiency and accelerating automotive thermal-system development.