13 results about "Added mass" patented technology

The invention discloses a method for solving free vibration of a three-dimensional structure under an equal water depth condition, and relates to the technical field of ocean engineering, the method comprises the following steps: discretizing a geometric model of the structure to obtain a finite element mesh model and a boundary element wet surface mesh model; constructing a boundary integral equation based on the boundary element wet surface grid model and a potential flow theory, introducing a finite water depth mirror image Green function without considering a free surface effect, and solving a flow field velocity potential of a structure in the equation under an equal water depth condition; calculating the additional mass generated by the fluid on the structure when the structure freely vibrates in the flow field based on the flow field velocity potential; and obtaining a free vibration equation of the structure according to the finite element mesh model, adding additional mass, and solving to obtain the vibration intrinsic mode and the vibration frequency of each order of the structure in the flow field. According to the method, the simulation requirement for the fluid-solid coupling effect of the structure in actual engineering can be met, simulation calculation can be carried out only by carrying out finite element modeling on the structure, and certain calculation precision is achieved.

According to the method, a multi-modal analytical model with the effects of surface waves and internal waves is established aiming at the density stratification phenomenon caused by gravity settlement and solar radiation heat effect in ocean engineering; a three-dimensional layered fluid global control equation set is constructed, a hyperbolic function combined vertical characteristic function piecewise expression is adopted to accurately characterize fluid bimodal propagation characteristics, a double-layer fluid bimodal dispersion equation is combined, a multi-body coupling matrix equation is introduced to process an inter-column wave scattering effect, and a multi-body coupling matrix equation is introduced to process the inter-column wave scattering effect. Cylindrical wave function coordinate transformation is realized by applying a Graf addition theorem, and a hydrodynamic integral expression containing additional mass and radiation damping is constructed based on a modal superposition principle. According to the method, the limitation of a traditional single-layer fluid model is broken through, the wave interference energy distribution rule under the surface wave-internal wave combined action is quantitatively analyzed, and the radiation force calculation precision and the engineering prediction applicability of the dense cylinder array in the complex marine environment are remarkably improved.

The invention relates to the technical field of band gap vibration reduction in a fluid environment, in particular to a band gap calculation method for a curve stiffened plate structure in the fluid environment, which comprises the following steps: constructing a curve stiffened plate band gap structure model in the fluid environment, carrying out finite element discretization on a curve stiffened plate and a fluid domain, and calculating the band gap of the curve stiffened plate. And establishing a mapping relation between the curve reinforcement rib node displacement and the substrate node displacement, constructing a structural balance equation after finite element discretization, applying a Bloch boundary condition and solving a band gap. According to the band gap calculation method for the curve stiffened plate structure in the fluid environment, the dynamic coupling equation of the solid domain and the fluid domain is established, the fluid additional mass effect and the fluid-solid interface interaction are clearly considered, and the problem of result deviation caused by neglecting the fluid influence in traditional stiffened plate band gap calculation is solved.

The invention relates to the technical field of dynamics, and discloses a method and device for determining the inherent frequency of a pumping and storing rotating wheel with fluid flowing considered. Finite element analysis is carried out on the rotating wheel in air, and the in-air vibration mode, the in-air inherent frequency, the structural modal quality and the structural modal rigidity of a target modal of the rotating wheel are obtained; the method comprises the following steps: firstly, carrying out finite element analysis on a runner in still water to obtain a still water vibration mode and a still water inherent frequency of a target mode of the runner, secondly, extracting a traveling wave vibration mode of the runner after mode splitting under a fluid relative rotation condition to obtain a node displacement amplitude and a node initial phase corresponding to the traveling wave vibration mode, and finally, calculating the node displacement amplitude and the node initial phase of the runner. Unsteady flow analysis is carried out through the fluid dynamics analysis model, the flowing water additional mass and the inherent frequency in the flowing water of the rotating wheel under the flowing water condition are obtained, then the influence of fluid flow on the rotating wheel modal parameters is comprehensively quantified, and the prediction precision of the inherent frequency of the pumping and storage rotating wheel is improved.

The invention discloses a numerical method for predicting aerodynamic force of a large-span bridge through a vortex structure around a flow field, and belongs to the field of bridge wind engineering. The method comprises the following steps of: simulating and generating a velocity field and vortex structure information around a flow field by utilizing computational fluid mechanics; determining geometric boundary conditions based on a vortex force diagram method, constructing and solving a hypothetical potential equation, and calculating a vortex force vector; finally, the additional mass force, the vortex pressure, the viscosity pressure and the friction force are calculated through integration, and the total aerodynamic force is synthesized. The method combines flow field information and aerodynamic force, can analyze contribution of different vortex structures, is suitable for a single box girder bridge and a multi-box girder bridge, has the advantages of being accurate in result, high in efficiency and small in resource occupation, can be used for flow separation aerodynamic force mechanism analysis, and solves the problem that a traditional pressure integral method cannot analyze the influence of a flow field.

This invention belongs to the field of fluid-structure interaction dynamics analysis technology, and specifically discloses a method and system for analyzing the dynamic characteristics of an acoustic-frequency resonant hybrid system. The method includes: introducing an external excitation force vector and a fluid feedback force vector into the dynamic control equations of the acoustic-frequency resonant hybrid system to form coupled dynamic equations; numerically characterizing the fluid feedback force using a multi-harmonic fitting method to obtain a fluid force model; based on the fluid force model, obtaining the dominant frequency component of the fluid force and mapping it equivalently to an additional mass parameter and an equivalent damping parameter; then fitting the optimal functional form of the additional mass parameter and the equivalent damping parameter relative to the excitation acceleration; updating the coupled dynamic equations based on the optimal functional form to achieve dynamic characteristic analysis under different excitation acceleration conditions. This invention can accurately analyze the dynamic characteristics of an acoustic-frequency resonant hybrid system under high-acceleration vibration environments to address nonlinear dynamic problems induced by fluid-structure interaction.

This invention discloses a method for analyzing the dynamic response of a multi-section, multi-compartment, damaged floating bridge under load. The method dynamically updates the liquid level in each compartment, the mass of water entering the compartment, its center of mass, and the change in moment of inertia of the bridge sections caused by water ingress, based on the size and location of the breach. After determining the position and inclination angle of each bridge section in a stable equilibrium state in still water, the method calculates the generalized added mass coefficient, radiation damping coefficient, and wave excitation force of the floating bridge system under water ingress conditions based on potential flow theory. Finally, it uses the multi-body time-domain hydrodynamic analysis equations to analyze the dynamic response of the damaged floating bridge under load. This invention constructs a theoretical framework for the dynamic response analysis of a damaged floating bridge in still water using multi-body dynamics methods, constructs a multi-section, multi-compartment water ingress model using the modified Bernoulli equation, and then uses potential flow theory to conduct time-domain hydrodynamic analysis, achieving efficient dynamic response prediction and improving calculation accuracy and efficiency.

The invention provides an anti-seismic evaluation method and device for a sluice gate of a nuclear power plant, electronic equipment and a storage medium. The anti-seismic evaluation method comprises the steps of obtaining gate structure parameters, pool geometric parameters and seismic oscillation parameters of a target sluice gate; according to the geometric parameters and the seismic oscillation parameters of the pool, calculating vertical dynamic water pressure, horizontal dynamic water pressure and liquid oscillation pressure acting on the target sluice gate; calculating the dynamic water load stress of the dynamic water load according to the vertical dynamic water pressure, the horizontal dynamic water pressure and the liquid oscillation pressure; calculating the structure inertia stress of the target sluice gate based on the water body additional mass, the gate structure parameters and the seismic oscillation parameters; the static stress of the target sluice gate under the static load is calculated according to the sluice gate structure parameters and the pool geometric parameters; calculating the target total stress of the target sluice gate according to the dynamic water load stress, the structural inertia stress and the static stress; and carrying out anti-seismic evaluation on the target sluice gate according to the target total stress. According to the invention, the calculation efficiency and accuracy of anti-seismic evaluation can be improved.

The present invention relates to a method, system and medium for seismic analysis of a fast reactor full core assembly. The method comprises: equivalently decomposing the full reactor nonlinear multi-component system into a series of linear single-component vibration systems; calculating the additional mass coefficient of the characteristic component based on numerical simulation to simulate the influence of fluid-solid coupling on the vibration of the component; establishing a finite beam unit model of a single core assembly that is independent of each other based on Euler-Bernoulli theory, connectors and additional mass coefficients; reducing the dimension of the single core assembly vibration system to a solution of a single degree of freedom system; calculating the vibration response of the single degree of freedom system in modal coordinates using a central difference method and converting it into a dynamic response in physical coordinates; and performing deflection analysis and contact analysis if the earthquake acceleration time history stops. The present invention rapidly solves the structural dynamic response under gap conditions, greatly improving the computational efficiency of the method.

The invention relates to a water turbine mechanical simulation method and device based on fluid additional mass and a medium, belongs to the technical field of water conservancy and hydropower engineering, and provides a technical scheme for solving the problem that a traditional flow-induced vibration algorithm based on an acoustic fluid unit is low in calculation efficiency. A steady-state flow velocity field in the flow channel and a steady-state flow velocity field pressure mean value are obtained through calculation; calculating the dry mode of the runner in the air to obtain generalized fluid additional mass, and calculating the inherent frequency and vibration mode of the runner in the fluid; performing Fourier spectrum analysis to screen out a main frequency, projecting the main frequency to a dry modal basis, solving a runner vibration generalized displacement equation, and calculating runner dynamic stress through modal superposition and transformation to a time domain; and solving the runner displacement and static stress. According to the method, the frequency domain of the steady-state dynamic response of the runner is calculated in the dry modal space of the runner based on the fluid additional mass, and the degree of freedom of the model is greatly reduced and the number of solving times of the dynamic equation is reduced in combination with Fourier frequency screening.

A calculation method for the hydrodynamic coefficients of the internal damping component of a tuned liquid damper, comprising the following steps: Step S11, under the action of a random load, respectively collect the wave height response signals of the free surface of the TLD through a plurality of wave gauges; Step S12, use the data-driven stochastic subspace method to identify the parameters of the wave height response signals to obtain the natural frequency and damping ratio of the TLD system; Step S13, establish the natural frequency ω T formula and damping ratio ζ T formula, Step S14, substitute the natural frequency of the TLD system into the natural frequency ω T formula for calculation to obtain the added mass coefficient C of the internal damping component of the TLD m , substitute the damping ratio of the TLD system into the damping ratio ζ T formula for calculation to obtain the drag coefficient C of the internal damping component of the TLD d . The hydrodynamic coefficients of the damping component obtained by the method of the present invention can be used to calculate the added mass and damping ratio generated by the damping component under the action of a random load, and for the equivalent mechanical model to analyze the dynamic response of the TLD under the action of a random load; and the method is simple and convenient, easy to implement, and applicable to the determination of the optimization design scheme of the damping component for the wind-induced vibration control of super high-rise buildings by the TLD.

This application relates to a method, device, and medium for simulating the mechanics of hydraulic turbines based on fluid-added mass, belonging to the field of hydraulic and hydropower engineering technology. Addressing the low computational efficiency of traditional flow-induced vibration algorithms based on acoustic-fluid elements, it provides a technical solution: constructing a structural mechanics simulation model and a fluid mechanics simulation mesh model, and calculating the steady-state velocity field and mean pressure within the flow channel; calculating the dry modes of the turbine runner in air to obtain the generalized fluid-added mass, and calculating the natural frequencies and mode shapes of the runner in the fluid; using Fourier spectrum analysis to select the main frequencies, projecting them onto the dry mode basis, solving the generalized displacement equation of the turbine vibration, and calculating the dynamic stress of the runner through modal superposition and transformation to the time domain; and solving for the turbine displacement and static stress. This application calculates the frequency domain of the turbine's steady-state dynamic response in the dry mode space based on fluid-added mass, and combined with Fourier frequency selection, significantly reduces the model's degrees of freedom and the number of times the dynamic equations are solved.

The invention discloses a composite hydrofoil load and structure response characteristic prediction method based on a fluid-solid coupling reduced-order model in the technical field of ocean engineering equipment, and the method comprises the steps: driving CFD simulation based on a broadband excitation signal to obtain hydrodynamic response data, and carrying out the system identification and training through an autoregressive exogenous model; establishing a continuous state space hydrodynamic reduction model; secondly, aiming at the composite material hydrofoil, calculating an anisotropic stiffness matrix of the composite material hydrofoil by combining three-dimensional modeling, finite element analysis and a classical laminated plate theory, introducing a Theodorsen theory and a fluid additional mass effect, and constructing a parameterized structure reduced-order model; and finally, coupling the hydrodynamic reduced-order model with the structural reduced-order model to form a parameterized hydroelastic fluid-solid coupling reduced-order model. According to the method, the efficiency and precision of fluid-solid coupling analysis of the composite hydrofoil are remarkably improved, and an effective numerical prediction tool is provided for stability design, frequency locking phenomenon avoidance and structure optimization of the hydrofoil.