Accurate aerodynamic measurements in the hypersonic flow of large aircraft models in tunnels have practical significance, but pose a significant challenge. Novel aerodynamic force measurement methods have been propose...Accurate aerodynamic measurements in the hypersonic flow of large aircraft models in tunnels have practical significance, but pose a significant challenge. Novel aerodynamic force measurement methods have been proposed,but lack theoretical support. The forms of the force signals techniques for signal processing and calculation of aerodynamics are especially problematic. A theoretical study is conducted to investigate the dynamic properties based on models of the draw-rod system and slender rods. The results indicate that the inertia item can be neglected in the rod governing equation;further, the solutions show that the signals of each rod are a combination of aerodynamic signals（with a constant value） and sine signals, which can be verified by experimental shock tunnel results. Signal processing and aerodynamics calculation techniques are also found to be achievable via the flat part of the signals.展开更多
Stiffness is one of the basic performance parameters for railway track. The efficient and accurate stiffness measurement has been considered as the foundation for further development of railway engineering, and theref...Stiffness is one of the basic performance parameters for railway track. The efficient and accurate stiffness measurement has been considered as the foundation for further development of railway engineering, and therefore has great theoretical and practical significance. Based on a summary of the connotation and measurement of track stiffness, the state of the art of measurement methods for track stiffness was analyzed systematically. The standstill measurement of track stiffness can be performed with the traditional jack-loading method, impact hammer method, FWD （falling weight deflectometer） method, and track loading vehicle method. Although these methods can be adopted in stiffness measurement for a section of railway track, they are not desirable owning to small range and low efficiency. In the recent 20 years, researchers have proposed many methods like unbalancedloading laser displacement method, deflection basin deformation rate method, and eccentricity excitation method to continuously measure track stiffness; however, these methods have drawbacks like poor accuracy, low speed, and insufficient data analysis. In this work, the merits and demerits of these methods were summarized, and optimization suggestions were presented. Based on the wave transmission mechanism and principle of vibration energy harvesting, an overall conception on continuous measurement of stiffness and long-term stiffness monitoring for special sections was proposed.展开更多
The design of a ship is a process facilitated by different parallel departments.Specialists from various disciplines jointly work on a project,eventually covering the entire process.Though simultaneously,these discipl...The design of a ship is a process facilitated by different parallel departments.Specialists from various disciplines jointly work on a project,eventually covering the entire process.Though simultaneously,these disciplines are often subject to a hierarchy,either clearly defined or dictated by necessity.Within these branches,despite a growing interest in enhancing the comfort on board ships,noise and vibration design is among the most sacrificed.Compared to hydrodynamic or structural modifications,efforts devoted to improving vibrational comfort are generally slightly impactful and costly.Consequently,these improvements are often relegated to the final stages of the design procedure.The underestimation of noise and vibrational comfort design can generate serious,unexpected issues emerging only in the advanced phases of the ship’s life,and post-construction interventions are often needed.This case is exemplified in the current study,where the crew of the research vessel Mintis,a catamaran-type hull,reported discomfort in the navigation wheelhouse.A measurement campaign was set up to assess the complaints of the operating personnel regarding the high vibrational levels.Subsequent to the measurements,a numerical simulation,specifically comprising a modal analysis,was conducted to investigate the nature of the disturbance and distinguish the underlying mechanism at its origin.This paper meticulously presents and discusses the strategy undertaken to analyze and solve the vibrational problem encountered on board,with particular attention to the criteria and the modeling considerations adopted.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11472281 and 11532014)
文摘Accurate aerodynamic measurements in the hypersonic flow of large aircraft models in tunnels have practical significance, but pose a significant challenge. Novel aerodynamic force measurement methods have been proposed,but lack theoretical support. The forms of the force signals techniques for signal processing and calculation of aerodynamics are especially problematic. A theoretical study is conducted to investigate the dynamic properties based on models of the draw-rod system and slender rods. The results indicate that the inertia item can be neglected in the rod governing equation;further, the solutions show that the signals of each rod are a combination of aerodynamic signals（with a constant value） and sine signals, which can be verified by experimental shock tunnel results. Signal processing and aerodynamics calculation techniques are also found to be achievable via the flat part of the signals.
基金supported by the project (51425804) of the National Science Fund for Distinguished Young Scholars of Chinathe National Natural Science Foundation of China (NSFC) under grants U1234201, U1334203, and 51378439
文摘Stiffness is one of the basic performance parameters for railway track. The efficient and accurate stiffness measurement has been considered as the foundation for further development of railway engineering, and therefore has great theoretical and practical significance. Based on a summary of the connotation and measurement of track stiffness, the state of the art of measurement methods for track stiffness was analyzed systematically. The standstill measurement of track stiffness can be performed with the traditional jack-loading method, impact hammer method, FWD （falling weight deflectometer） method, and track loading vehicle method. Although these methods can be adopted in stiffness measurement for a section of railway track, they are not desirable owning to small range and low efficiency. In the recent 20 years, researchers have proposed many methods like unbalancedloading laser displacement method, deflection basin deformation rate method, and eccentricity excitation method to continuously measure track stiffness; however, these methods have drawbacks like poor accuracy, low speed, and insufficient data analysis. In this work, the merits and demerits of these methods were summarized, and optimization suggestions were presented. Based on the wave transmission mechanism and principle of vibration energy harvesting, an overall conception on continuous measurement of stiffness and long-term stiffness monitoring for special sections was proposed.
文摘The design of a ship is a process facilitated by different parallel departments.Specialists from various disciplines jointly work on a project,eventually covering the entire process.Though simultaneously,these disciplines are often subject to a hierarchy,either clearly defined or dictated by necessity.Within these branches,despite a growing interest in enhancing the comfort on board ships,noise and vibration design is among the most sacrificed.Compared to hydrodynamic or structural modifications,efforts devoted to improving vibrational comfort are generally slightly impactful and costly.Consequently,these improvements are often relegated to the final stages of the design procedure.The underestimation of noise and vibrational comfort design can generate serious,unexpected issues emerging only in the advanced phases of the ship’s life,and post-construction interventions are often needed.This case is exemplified in the current study,where the crew of the research vessel Mintis,a catamaran-type hull,reported discomfort in the navigation wheelhouse.A measurement campaign was set up to assess the complaints of the operating personnel regarding the high vibrational levels.Subsequent to the measurements,a numerical simulation,specifically comprising a modal analysis,was conducted to investigate the nature of the disturbance and distinguish the underlying mechanism at its origin.This paper meticulously presents and discusses the strategy undertaken to analyze and solve the vibrational problem encountered on board,with particular attention to the criteria and the modeling considerations adopted.
