Kinematic analyses of wave–packet structures in non-isothermal jet flows: Effects of length scales
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A kinematic wave–packet sound-source model is developed for non-isothermal jets based on large eddy simulation results of subsonic jets at temperature ratios 0.86, 1.0, and 2.7. To find the suitable variable for the sound-source model, coherent structures in these jets are extracted by leading modes of the proper orthogonal decomposition (POD), and they are classified according to spatial–temporal features. To extend the model, an approach is proposed to represent the growth and decay length scales separately by a single continuous function. Applying such function, the acoustic affections are discussed for the variable length scales of amplitude envelope, L, and coherence, Lc. The results show that the jet temperature desynchronizes the leading POD modes of radial velocity, pressure, and density, and the jet temperature changes the density mode from radial puffs into stripes or ridges. The axisymmetric component of the pressure clearly presents a train of radiant waves, as captured by its leading spectral-POD mode at the peak radiation frequency. Therefore, this pressure component is employed for modeling. In the wave-number domain, the elongation of L stretches the cross-spectral density (CSD) of the source signal, denoted by CSD(k1, k2), along the k1- and k2-axes; the decay of Lc stretches the CSD along the diagonal of the axes. Both of them tend to spread the CSD into a radiant region near the origin point, so as to enhance the radiation. The radiation seems insensitive to the variation of the L, as it only slightly distorts the CSD in the radiant region.Keywords:
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This paper deals with kinematic pairs in the most general sense, and, in particular, with those used in gear design. The paper begins with a brief overview of the earlier performed research in the field. Different kinds of kinematic pairs are distinguished, namely, point-contact kinematic pairs, line-contact kinematic pairs, and surface-to-surface-contact kinematic pairs. Contact geometry of functional surfaces in kinematic pairs is involved into the analysis aiming more in detail analysis of design, and the development of a scientific classification of kinematic pairs. A scientific classification of all possible kinds of kinematic pairs is developed. All known designs of kinematic pairs are covered by the classification. Moreover, kinematic pairs of all notknown yet designs are also covered by the classification. This means that the proposed classification of kinematic pairs possesses predictive properties.
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The structure of parallel kinematic machines of SKM400 was introduced,its kinematic model was established,and the position and velocity were calculated.Based on Jacobian,kinematic performance was evaluated via example.The SKM400 can be widely used in manufacturing.
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Some data about kinematic calibration of parallel kinematic machine was analyzed and summarized,the machining error of parallel kinematic machine was explained,the kinematic calibration method was classified,some suggest on the study of kinematic calibration was put forward,and it was indicated that kinematic calibration is an effective method to improve the static accuracy of parallel kinematic machine.
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Abstract This paper presents a comparative analysis of two kinematic structures of the support system (with supports with bilateral and unilateral constraints), which were used in an experimental model of a crane. The computational model was developed by using the ADAMS software. The impact of the kinematic structure of the support system on selected kinematic and dynamic values that were recorded during the slewing motion was analysed. It was found, among other things, that an increased number of degrees of freedom of the support system leads to multiple distortions of time characteristics of kinematic and dynamic quantities.
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This dissertation presents a novel task-based approach towards computer-aided kinematic design of spherically constrained kinematic chains. Based on a detailed review of the state-of-the-art in theoretical kinematics, linkage design theory as well as computer-aided kinematic design new kinematic synthesis and analysis methods as well as a general CAD-integrated kinematic design process were developed. An example of a spatial kinematic motion task is used to demonstrate theory and methods.
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This study aims to propose a kinematic analysis approach for a novel vibratory bowl feeder, and verify its feasibility by kinematic simulation. First, the novel design is presented, and its advantages compared with conventional feeders are described. Moreover, the equations for kinematic analysis are derived. Finally, the solid model for the proposed design is established, and then kinematic simulation is performed by ADAMS software. The simulation results indicate that the proposed design can effectively advances the part with high efficiency.
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In addressing the motion of machine parts, machines and equipment it is necessary to first create a kinematic model. Kinematic model of a device schematically captures all its properties which are essential in kinematic analysis. This article deals with kinematic analysis of a simple mechanism executing a rotational movement. We analyzed the movement of its end points. Numerical solution was implemented by classical kinematics using different coordinate systems, while model mechanism has been also modeled and solved in the program MSC Adams. The result of the computer simulation is designation of the searched kinematic parameters and the other required parameters of the solved model. Solutions are time kinematic variables over time, which are shown graphically.
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This chapter presents a systematic formulation for expressing the kinematic relationships concerning a mechanical system such as a manipulator or a mechanism. A kinematic chain is such that its members are connected serially. The kinematic chains are divided into two categories as kinematic branches (i.e. open kinematic chains) and kinematic loops (i.e. closed kinematic chains). A general rigid body system may consist of one or several kinematic chains. The main purpose of the chapter is to derive the necessary equations in suitable forms as a preparation for a subsequent detailed kinematic analysis of the system. It includes two comprehensive examples. In the first, the three-joint arm of a spatial serial manipulator is studied as a typical open kinematic chain. In the second, a spatial slider-crank mechanism is studied as a typical closed kinematic chain. The necessary kinematic equations are derived in order to express the position, velocity, and acceleration relationships.
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This paper introduces the concepts of “Kinematic Moment” and “ Kinematic inertia” to study the structure based velocity and acceleration characteristics respectively of kinematics chains in a comparative sense. Example problems are included. Keywords: Kinematic moment: Kinematic Inertia, Kinematic Chains, Velocities, Accelerations.
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