An inter-comparison of three urban wind models using Oklahoma City Joint Urban 2003 wind field measurements

Three wind models are compared to near-surface time-averaged wind measurements obtained in downtown Oklahoma City during the Joint Urban 2003 Field Campaign. The models cover several levels of computational approximation and include in increasing order of computational demand: a mass-consistent empirical-diagnostic code, a Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) model, and a Large Eddy Simulation (LES) CFD code. The models were run with identical inlet and boundary conditions using the same grid resolution; the choice of the specific computational set-up reflects demands for fast-response models, although it may be a sub-optimal choice for the more complex models. A qualitative comparison of the model-computed flow fields with the Joint Urban 2003 wind measurements shows that all three models compare favorably to the near-surface wind measurements in many locations, although there are often instances of winds being calculated poorly in specific locations. The CFD models, however, had clearly superior looking flow fields, whereas the empirical-diagnostic code produced fields that were less smoothly varying. The inter-comparison exercise was supported by point-by-point quantitative comparisons of the wind speed and wind direction and with statistical measures. The RANS-CFD code, for example, was within 50% of the measured wind speed 62% of the time as compared to 53% for the LES model and 49% for the empirical-diagnostic code. For wind direction, the RANS-CFD code was within 30° of the measured wind direction 58% of the time as compared to 50% for the LES code and 43% for the empirical diagnostic code. It is noticeable that throughout the various IOP cases examined, and under the specific computational set-up used in the simulations for fast-response needs, there is no clear superiority of one model over another. In addition, for the LES model, which in theory should provide the most realistic representation of the flow field, it appears that further to the sub-optimal computational set-up, as well as the uncertainty and natural variability persistent in the real world, has resulted in diminished performance.     

FL413柴油机缸内局部瞬态热流的实验研究

本文运用快速响应的表面温度与热流传感器,测量了FL413柴油机缸盖火力面15点的瞬时温度与相对应冷却侧稳定温度。采用热传导反问题求解方法,得到了缸内气体与缸盖表面局部瞬态热流的实验结果。实验结果表明,缸内局部瞬态热流存在明显的差异,以往采用的缸内传热经验公式需要进一步研究修正。     

Security-constrained expansion planning of fast-response units for wind integration

This paper proposes a stochastic expansion planning of fast-response thermal units for the large-scale integration of wind generation (WG). The paper assumes that the WG integration level is given and considers the short-term thermal constraints and the volatility of wind units in the planning of fast-response thermal units. The new fast-response units are proposed by market participants. The security-constrained expansion planning approach will be used by an ISO or a regulatory body to secure the optimal planning of the participants’ proposed fast-response units with the WG integration. Random outages of generating units and transmission lines as well as hourly load and wind speed forecast errors are modeled in Monte Carlo scenarios. The Monte Carlo simplification methods are introduced to handle large-scale stochastic expansion planning as a tradeoff between the solution accuracy and the calculation time. The effectiveness of the proposed approach is demonstrated through numerical simulations.     

快速响应红外探测器自适应降噪

为了在不降低快速响应热释电探测器响应速度的同时抑制器件的振动干扰,通过对快速响应热释电红外探测器的振动噪声机理和输出电信号的频谱分析,提出了数字降噪方案,并用基于FPGA的硬件电路来实现.文中还介绍了硬件的结构和FPGA代码实现,给出了降噪之后的实际效果.     

快速响应红外探测器数字降噪研究

通过分析快速响应热释电红外探测器的振动噪声机理和输出电信号的频谱,得到相应结果。根据结果本文提出一种新颖的数字降噪方案,并采用基于FPGA的硬件电路将其实现,在文中对硬件的结构和其中的FPGA代码实现进行了介绍,最后本文给出了降噪之后的实际效果。