Experimental Validation Data for CFD of Steady and Transient Mixed Convection on a Vertical Flat Plate

Simulations are becoming increasingly popular in science and engineering. One type of simulation is Computation Fluid Dynamics (CFD) that is used when closed forms solutions are impractical. The field of Verification & Validation emerged from the need to assess simulation accuracy as they often contain approximations and calibrations.

Validation involves the comparison of experimental data with simulation outputs and is the focus of this work. Errors in simulation predictions may be assessed in this way. Validation requires highly-detailed data and description to accompany these data, and uncertainties are very important.

The purpose of this work is to provide highly complete validation data to assess the accuracy of CFD simulations. This aim is fundamentally different from the typical discovery experiments common in research. The measurement of these physics was not necessarily original but performed with modern, high fidelity methods. Data were tabulated through an online database for direct use in Reynolds-Averaged Navier Stokes simulations. Detailed instrumentation and documentation were used to make the data more useful for validation. This work fills the validation data gap for steady and transient mixed convection.

The physics in this study included mixed convection on a vertical flat plate. Mixed convection is a condition where both forced and natural convection influence fluid momentum and heat transfer phenomena. Flow was forced over a vertical flat plate in a facility built for validation experiments. Thermal and velocity data were acquired for steady and transient flow conditions. The steady case included both buoyancy-aided and buoyancy-opposed mixed convection while the transient case was for buoyancy-opposed flow. The transient was a ramp-down flow transient, and results were ensemble-averaged for improved statistics. Uncertainty quantification was performed on all results with bias and random sources.

An independent method of measuring heat flux was devised to assess the accuracy of commercial heat flux sensors used in the heated wall. It measured the convective heat flux by the temperature gradient in air very near the plate surface. Its accuracy was assessed by error estimations and uncertainty quantification.

模拟在科学与工程领域的应用日益普及。其中一类模拟为计算流体动力学（Computation Fluid Dynamics，CFD），该方法适用于闭式解析解难以获取的场景。验证与确认（Verification & Validation）领域正是因评估模拟精度的需求应运而生——由于模拟过程通常包含近似处理与校准环节，其结果的准确性需要被严格校验。

验证环节涉及将实验数据与模拟输出结果进行对比，这也是本研究的核心内容。通过该方式可对模拟预测的误差进行评估，而验证工作需要配套详实的数据与数据说明，同时不确定性分析也至关重要。

本研究的核心目标是提供完备的验证数据，用于评估计算流体动力学模拟的精度。这一研究定位与学界常见的探索性实验截然不同。本研究中的物理量测量并非原创性工作，而是采用现代高保真方法完成的。所有数据均通过在线数据库整理制表，可直接应用于雷诺平均纳维-斯托克斯（Reynolds-Averaged Navier Stokes）模拟。研究中采用了精细化的仪器配置与文档记录，以提升数据在验证工作中的实用性。本研究填补了定常与非定常混合对流（mixed convection）领域的验证数据空白。

本研究的物理场景为竖直平板上的混合对流。混合对流指强制对流与自然对流共同影响流体动量与传热现象的工况。研究在专为验证实验搭建的试验装置中，使气流横向掠过竖直平板，并针对定常与非定常流动工况采集了热参数与速度数据。定常工况涵盖了浮力助推与浮力阻抑两种混合对流类型，而非定常工况仅针对浮力阻抑流动。该非定常过程为流量渐减瞬态，结果通过集合平均以优化统计特性。所有实验结果均开展了不确定性量化分析，涵盖系统偏差与随机误差两类来源。

本研究设计了一种独立的热流测量方法，用于评估加热壁面所使用的商用热流传感器的精度。该方法通过紧贴平板表面的空气温度梯度来计算对流热流，其精度通过误差估算与不确定性量化进行了验证。