In June, 2004 and February, 2007, in field tracer studies were conducted on the Hollywood and South Central outfalls, using sulfur hexafluoride (SF6) as a tracer. The objective of these studies was to determine if the...In June, 2004 and February, 2007, in field tracer studies were conducted on the Hollywood and South Central outfalls, using sulfur hexafluoride (SF6) as a tracer. The objective of these studies was to determine if the tracer could be detected in the farfield at significant distance, and if so, could this data be used to construct a model of the farfield plume. Prior models for farfield plume movement do not appear to comport well with the conditions in southeast Florida. Extensive research was conducted in southeast Florida on 4 outfalls, which led to the development of nearfield dilution equations for same. However farfield modeling of outfall plumes was difficult to accomplish because the tracers used are not detectable for significant distances. The SF6 resolved that problem and as a result the Hollywood outfall was used to construct a model. Two methods were investigated for modeling the plume, 1) the Eureqa formulation method and 2) the Gamma-Curve method. The concentrations in the x-y plane were first found by using the Eureqa formulation to calculate the concentration at each grid point given its depth and the concentration of the centerline at the same latitude. The plume models were generated using MATLAB that matched with the results actually seen in the field.展开更多
Basic models of the farfield waves created by a monohull ship or a catamaran that travels at a constant speed in calm water of uniform finite depth are considered.A classical basic model is the 1-point ship model intr...Basic models of the farfield waves created by a monohull ship or a catamaran that travels at a constant speed in calm water of uniform finite depth are considered.A classical basic model is the 1-point ship model introduced by Kelvin in 1887 for deep water and extended to uniform finite water depth by Havelock in 1908.Another basic model is the 2-point ship model,which considers the two dominant waves created by the bow and the stern of a monohull ship or by the twin bows of a catamaran,and therefore accounts for main wave interference effects.These 2-point ship models contain information that cannot be found in the classical patterns for the 1-point ship model commonly used since Kelvin.In particular,whereas Havelock’s classical wave patterns for the 1-point model only depend on the Froude number based on the water depth,the farfield waves for the 2-point models of a monohull ship or a catamaran also depend on the Froude number associated with the length of the monohull ship or the spacing between the twin hulls of the catamaran.Moreover,the‘apparent wake angles’associated with the highest waves that result from constructive wave interferences can greatly differ from the cusp or asymptote angles of Havelock’s wave patterns.展开更多
针对目前带探头补偿的平面近远场变换中,探头H面方向图对远区副瓣引入较大误差的情况,结合国内传统的E面电场法和K.T.Selvan提出的边缘电流逼近法各自的优点,利用混合算法研究了一种新的探头方向图逼近公式,并将其应用于平面近场测试中...针对目前带探头补偿的平面近远场变换中,探头H面方向图对远区副瓣引入较大误差的情况,结合国内传统的E面电场法和K.T.Selvan提出的边缘电流逼近法各自的优点,利用混合算法研究了一种新的探头方向图逼近公式,并将其应用于平面近场测试中。通过在某大型微波暗室对一频段阵列天线进行实际测量,分别用E面电场法、边缘电流逼近法以及新的方法进行带探头补偿的近远场变换。最后,将各种方法与实际测试结果进行比较,求得其误差曲线,并在全域的角度分析各种方法的-50 d B超低副瓣精度。结果表明,此方法集合了前两种方法的优点,相比E面电场法,远区副瓣精度提高了8.2 d B,整个角域内副瓣精度提高了1.13 d B;相比边缘电流逼近法,近区副瓣精度提高了0.89d B,整个角域内副瓣精度提高了0.87d B。展开更多
文摘In June, 2004 and February, 2007, in field tracer studies were conducted on the Hollywood and South Central outfalls, using sulfur hexafluoride (SF6) as a tracer. The objective of these studies was to determine if the tracer could be detected in the farfield at significant distance, and if so, could this data be used to construct a model of the farfield plume. Prior models for farfield plume movement do not appear to comport well with the conditions in southeast Florida. Extensive research was conducted in southeast Florida on 4 outfalls, which led to the development of nearfield dilution equations for same. However farfield modeling of outfall plumes was difficult to accomplish because the tracers used are not detectable for significant distances. The SF6 resolved that problem and as a result the Hollywood outfall was used to construct a model. Two methods were investigated for modeling the plume, 1) the Eureqa formulation method and 2) the Gamma-Curve method. The concentrations in the x-y plane were first found by using the Eureqa formulation to calculate the concentration at each grid point given its depth and the concentration of the centerline at the same latitude. The plume models were generated using MATLAB that matched with the results actually seen in the field.
文摘Basic models of the farfield waves created by a monohull ship or a catamaran that travels at a constant speed in calm water of uniform finite depth are considered.A classical basic model is the 1-point ship model introduced by Kelvin in 1887 for deep water and extended to uniform finite water depth by Havelock in 1908.Another basic model is the 2-point ship model,which considers the two dominant waves created by the bow and the stern of a monohull ship or by the twin bows of a catamaran,and therefore accounts for main wave interference effects.These 2-point ship models contain information that cannot be found in the classical patterns for the 1-point ship model commonly used since Kelvin.In particular,whereas Havelock’s classical wave patterns for the 1-point model only depend on the Froude number based on the water depth,the farfield waves for the 2-point models of a monohull ship or a catamaran also depend on the Froude number associated with the length of the monohull ship or the spacing between the twin hulls of the catamaran.Moreover,the‘apparent wake angles’associated with the highest waves that result from constructive wave interferences can greatly differ from the cusp or asymptote angles of Havelock’s wave patterns.
文摘针对目前带探头补偿的平面近远场变换中,探头H面方向图对远区副瓣引入较大误差的情况,结合国内传统的E面电场法和K.T.Selvan提出的边缘电流逼近法各自的优点,利用混合算法研究了一种新的探头方向图逼近公式,并将其应用于平面近场测试中。通过在某大型微波暗室对一频段阵列天线进行实际测量,分别用E面电场法、边缘电流逼近法以及新的方法进行带探头补偿的近远场变换。最后,将各种方法与实际测试结果进行比较,求得其误差曲线,并在全域的角度分析各种方法的-50 d B超低副瓣精度。结果表明,此方法集合了前两种方法的优点,相比E面电场法,远区副瓣精度提高了8.2 d B,整个角域内副瓣精度提高了1.13 d B;相比边缘电流逼近法,近区副瓣精度提高了0.89d B,整个角域内副瓣精度提高了0.87d B。
