Support Structure Model Research Articles

Time‐Frequency Analysis of Experimental and Analytical Rotor Thrust during a Rotor Speed Change

A study was conducted examining a small-scale, two‐bladed rotor undergoing a change in rotor speed. The data acquired consists of time histories of nonstationary signals; therefore, a Stockwell transform was employed to analyze the data in lieu of traditional Fourier transform-based methods. The analysis included extraction of time‐varying frequency content of the rotor thrust and hub motion, instantaneous rotor speed, damping ratios, and instantaneous phase difference between thrust and hub motion. This work is divided into two parts. First, an analytical study was conducted to understand how rotor transient response, determined using a time‐marching solution, is affected by the inclusion of a simplified elastic support structure model, and is used to demonstrate the utility of the Stockwell transform. The second part of the study compared the results from an analytical model of the NASA Multirotor Test Bed (MTB) undergoing a rotor speed change to wind tunnel data. The current analytical model of the MTB, including an elastic support structure, properly predicted the measured trends in the frequency content of the thrust; however, it underpredicted the amplitude of these unsteady loads.

On the experimental dynamic substructuring of rotating machine foundations

The dynamic behavior of a rotating machine consists not only of the response of the shaft, but it also contains information of all supporting structures and equipment interacting with the rotor. These support structures, also named foundations, can add substantial influence on the machine operational behavior, hence it becomes necessary to dynamically characterize its components. This study presents the application of substructuring techniques in assembling a supporting structure model for a rotating machine and presents a novel formulation of the mixed coordinates method, which is used to connect rotor and foundation. This foundation model is validated against the actual physical foundation and provides an efficient way to analyze and optimize the behavior of such systems. The robustness of the substructuring technique is demonstrated by comparing the responses of the global system solved with both the dynamically assembled and experimentally measured supporting structures in free-free and clamped conditions. The simulations reveal important phenomena of the complete system, including the presence of structural modes in the Campbell diagrams and in displacement responses. The technique allows flexibility in the design of numerical foundations without requiring physical mounting and measurements.

Experimental study of structural vibration control of 10-MW jacket offshore wind turbines using tuned mass damper under wind and wave loads

As slender structures, offshore wind turbines (OWTs) are prone to vibration and deformation under wind and waves. Tuned mass dampers (TMDs) have become among the most promising vibration-mitigation methods owing to their simplicity and practicability. To study the vibration control effect of a TMD on a jacket OWT under wind and wave conditions, we conducted a fully coupled dynamic model test of a 1/75 scale jacket OWT with and without a TMD. The physical model of the jacket OWT included scaled rotor-nacelle assembly (RNA) and support structure models. For the scaled RNA model, a redesigned blade model was used to ensure similarity of the aerodynamic thrust loads without modifying the scaled test winds. Drivetrain and pitch-control system models were designed to simulate the operating state of an actual OWT. The support structure model was established based on the hydro-structural elastic similarity. Furthermore, a TMD model was designed and manufactured based on the first mode of the scaled OWT. A fully coupled dynamic model test of a 10 MW jacket OWT with a TMD under wind and wave conditions was performed, and the vibration-mitigation performance of the designed TMD model on the structural responses of the scaled OWT model was evaluated.

Experimental study of dynamic characteristics of an ultra-large jacket offshore wind turbine under wind and wave loads using aero-hydro-structural elastic similarities

Owing to the difficulties in the scaled rotor-nacelle assembly (RNA) and support structure design, and alleviation of small scaling effects, the limited dynamic model tests are conducted for the jacket offshore wind turbines (OWTs), which are extensively constructed in the offshore wind farms located in the depth of 40–50 m. To address this limitation, an integrated test method based on aero-hydro-structural elastic similarities is proposed in this study. It comprises a performance-scaled RNA model and a scaled support structure model. A redesigned blade model is adopted in the scaled RNA model to ensure the similarities of aerodynamic thrust loads without modifications of the scaled test winds. Moreover, auxiliary scaled drivetrain and blade pitch control are designed to simulate the operational states of a practical OWT. The scaled model of the OWT support structure is fabricated based on the joint hydro-structural elastic similarity, and the small scaling effects are mitigated by introducing sectional bending stiffness similarities. Subsequently, the dynamic model tests of an ultra-large jacket OWT under wind-only, wave-only, and combined wind and wave conditions are carried out. The accuracy of the fabricated OWT test model is validated based on the recorded responses, and the influence of the dominant frequencies on the dynamic responses of the OWT model is quantitatively evaluated using the wavelet packet-based energy analysis method. Further, the coupling mechanisms of the scaled OWT model under typical wind and wave loads are investigated, and the interactions between the environmental loads and OWT motions are proved.

Experimental Study of Ultra-Large Jacket Offshore Wind Turbine under Different Operational States Based on Joint Aero-Hydro-Structural Elastic Similarities

The jacket substructure is generalized for offshore wind farms in the southeastern offshore regions of China. The dynamic characteristics and coupling mechanisms of jacket offshore wind turbines (OWTs) have been extensively investigated using numerical simulation tools. However, limited dynamic model tests have been designed and performed for such types of OWTs. Therefore, the coupling mechanisms of jacket OWTs that are determined using numerical methods require further validation based on experimental tests. Accordingly, an integrated scaled jacket OWT physical test model is designed in this study. It consists of a scaled rotor nacelle assembly (RNA) and support structure model. For the scaled RNA model, a redesigned blade model is adopted to ensure the similarity of the aerodynamic thrust loads without modifying the scaled test winds. Auxiliary scaled drivetrain and blade pitch control system models are designed to simulate the operational states of a practical OWT. The scaled model of the OWT support structure is fabricated on the basis of the joint hydro-structural elastic similarities. A sensor arrangement involving a three-component load cell and acceleration sensors is used to record the OWT thrust loads and model motions, respectively. Then, dynamic model tests under typical scaled wind fields are implemented. Furthermore, the coupling mechanisms of the OWT model under various test winds are investigated using the wavelet packet method, and the influences of inflow winds, operational states, and mechanical strategies are introduced.

Design and development of a novel additively manufactured geothermal heat exchanger

The existing geothermal heat exchangers pose a complex installation process and occupy large spaces which can potentially be cost-prohibitive to many potential users. In the present study, an additively manufactured heat exchanger was designed and developed to address this issue. The designed heat exchanger can be integrated with conventional geothermal heating and cooling systems for improved efficiency and easy installation. The additively manufactured heat exchanger developed in the present study eliminates the current need to excavate the soil and install the long piping as conventionally required for the existing geothermal systems. The prototype of the proposed geothermal heat exchanger was designed using CREO software and fabricated using the direct metal laser sintering technique (DMLS) to be integrated into a heat pump to exchange heat between a constant temperature of a water bath circulator and a water heat sink. Furthermore, the support structure model generated for metal printing of the proposed geothermal heat exchanger was exposed and discussed. Two customized geothermal heating and cooling modes were separately developed to evaluate the heat transfer performance of the heat exchanger analytically and numerically. Using the analytical approach, the system sizing was designated based on the metal additive manufacturing and thermal considerations, and then average heat transfer coefficients and pressure drops were estimated for a range of mass fluxes lying in the transitional and turbulent regimes. The distributions of wall temperature, fluid's bulk temperature, and fluid's velocity along the helically-coiled channel of the heat exchanger was also investigated numerically using the COMSOL-Multiphysics. Lastly, a detailed cost analysis was conducted to estimate the total cost per part for the prototype fabricated using the DMLS technology. Novelty Statement A novel ground-source heat exchanger was additively fabricated using the direct metal laser sintering (DMLS) technique. The unique compact screw-type design eliminates the need of excavating soil and features easy installation with less maintenance costs. Heat transfer characteristics of the proposed design were evaluated analytically and numerically. The proposed geothermal heat exchanger contributes effectively to the deployment of sustainable energy systems.

Design and Development of a PCM-Based Two-Phase Heat Exchanger Manufactured Additively for Spacecraft Thermal Management Systems

For spacecraft thermal management systems, it is crucial to diminish the overall mass of on-board thermal storage system and minimize the temperature fluctuations when the environmental temperature changes drastically. Since there is no atmosphere in outer space, heat can only be rejected to space using radiation (e.g., radiators). The heat sink conditions, and the heating power subjected to be rejected vary continuously at the orbiting stage of the spacecraft. Without thermal storage capability, the radiator is required to be large enough to release the highest power at the hottest of the heat sink. By engaging and integrating phase-change materials (PCMs) into a passive two-phase heat exchanger, the radiator can be designed and sized for the average rather than the maximum power. To meet the NASA needs, the prototype developed and fabricated in the present study is a novel two-phase heat exchanger that integrates PCMs within a vapor chamber through multiple thin drawers loaded with bulk PCM. The entire solid structure of the prototype is manufactured additively using Maraging Steel with the Direct Laser Metal Sintering (DLMS) technique. The chosen working fluid is Methanol to undertake two-phase heat transfer via saturated vapor from the heated surface of evaporator to the condenser surface, and the condensate then returns back to the heated region and keeps recirculated using the capillary pumping pressure performed by the wick structure without any reliance on the gravitational magnitudes. Depending on the heat sink temperature and PCM melting temperature, the developed heat exchanger can either function as a thermal capacitor or a two-phase heat exchanger with thermal storage capability, that is, two modes of operation to be engaged within the spacecraft's launching/landing stages or orbiting stage, respectively.In the present study, the geometry and number of the PCM-loaded drawers enclosed inside the heat exchanger's casing are optimized based on the mass ratio (the ratio of PCM mass to the total heat exchanger mass), additive manufacturing (AM) constraints, and total thermal resistances imposed on the system for either of the operation modes. The AM printed prototype with its all components are also represented along with technical drawings and specifications. Furthermore, the support structure model generated for metal printing of the proposed heat exchanger will be exposed and discussed. The wick structure design procedure is also presented and its main performance characteristics (e.g., effective pore size, effective thermal conductivity, porosity, and permeability) are reported to analytically examine the capillary pumping limit for the proposed heat exchanger.

Numerical simulation study on the mechanical behavior of shale core and reservoir rock mass

AbstractAfter the hydraulic fracturing of the shale reservoir, the stress field changes during the mining process. The stress sensitivity of the reservoir affects its development capabilities. Moreover, the stress sensitivity of shale reservoirs obtained by various researchers using different experimental methods is not uniform. This study analyzes the physical background differences between reservoir rock mass and experimental core. In this study, we establish the “support structure model” of the reservoir and show that the reservoir rock body has a structural overall effect, such that the supporting effect of the surrounding rock on the overlying strata is very strong. At the same time, we also establish the transverse isotropic numerical model of the shale reservoir on the basis of the real physical background of the reservoir and the experimental physical core model on the basis of the real physical background of the core test. This study shows that the equivalent mechanical behavior of the core test in the holder is pure core compression without the support and pull of the whole rock mass structure. In the real reservoir, the reservoir rock mass has significant structural effect. The actual compression change of real reservoir mining is less than the pure compression displacement of the experimental test core. The core stress sensitivity of the conventional experimental test does not directly describe the true stress‐strain effect of the macroscopic reservoir rock mass as a structural whole. A laboratory stress‐sensitive test apparatus and method that is equivalent to the physical background of a real reservoir needs to be improved or designed.

Research on high performance support technology of space-based large aperture mirror

A three-point back support structure including cone sleeve, flexible structure and adjustable pad is designed for the space-based mirror support to meet the requirements of small surface shape error, high supporting reliability and stability, of which in-depth study on support principle and engineering realization is conducted in this paper. The error sources which influence the surface shape error of the mirror subassembly with three-point back support is summarized. The mechanism of surface shape variation caused by various error sources is studied. The support structure with high stiffness for alleviating the surface shape error caused by various error sources is designed, which can increase the fundamental frequency of mirror subassembly and protect it from yield failure under the condition of dynamic load. Firstly, the static and dynamic simulation of the three-point back support structure model is carried out by means of finite element analysis. Then the dynamic and partial static experiments are performed using aluminum mirror and actual supporting structure. The results show that the surface shape error of mirror with the three-point support structure is superior to λ/80(λ = 632.8 nm), the displacement of mirror is smaller than 0.015 mm, the inclination angle is smaller than 2″, the mass of the mirror subassembly is smaller than 310 kg. The mirror subassembly has a reasonable modal distribution, the fundamental frequency is 128 Hz, which is much higher than the requirement of 120 Hz. The maximum magnification of the mirror assembly excited by the sinusoidal vibration and the random vibration is 2.51and the maximum stress is 286 MPa under the same working condition, which is much lower than the yield limit of the selected material. A kind of segmented metering assembly method is formed and applied to make sure 2 m space-based large-aperture mirror has lower surface shape error according to the theoretical research results in this paper which the surface shape error of the space-based large-aperture mirror supported by three-point on the back which optical axis is in the horizontal direction in test, installation and adjustment is very sensitive to the deviation between rotating shaft of flexible structure and the neutral plane of the mirror in the direction of the optical axis.

Modeling and Simulation Active Vibration Control of Flexible Solar Wing Support Structure

In this paper, the flexible solar wing support structure is taken as the research object, and the vibration is actively controlled by the piezoelectric material. In this paper, the Euler-Bernoulli beam theory is used to simplify the overall model structure. The principle of Language and the hypothetical modal method are used to derive the dynamic model of the piezoelectric flexible system. The obtained system dynamics model was simulated by PID control, and good results were obtained.

Experiment on Weight Efficient Support Structure by using Dynamic Opinionto Accommodate a Typical Sensor on Spacecraft

An artificial satellite is a human made structure, which is put into space around any planetary body to gather data and impart the equivalent information to ground stations. There is a huge requirement of several types of satellite sensors which are to be mounted on spacecraft or Satellite payloads. To accommodate sensors on Spacecraft, mounting structural elements are needed to support them. This project is mainly focused on the study of those mounting configurations with modeling and analysis of support structure used to mount Sensor in aerospace application. Different configuration of support structure modeled based on the frequency (100 Hz). These models were analyzed to optimize the mass. Work involves modal analysis of the structure made of aluminum and composite material (CFRP). The configuration of mounting structure for sensors is based on various constraints like interface requirements, functional requirement of sensor, stiffness, strength and most importantly the mass. Various configurations of the support structure have to be studied using modeling and analysis software keeping in view the stiffness requirement with minimum mass. For efficient design, composite materials are considered. Normal modal analysis will be carried out to understand the dynamic characteristics of the Mounting structure and the supporting structure was modeled using Al7075 and CFRP (Composite) materials and the results are compared in the present study

Analysis of the frame design of the subcompact racing car of go-kart class

The article presents the design features of subcompact small-capacity racing car of kart class. The issues of the strength of the supporting structure are considered. The main strength characteristics of the material AISI-1020 are presented, which was used in the design of the frame chassis. A conceptual block diagram of a methodology for designing a supporting structure model using engineering analysis methods (finite element modeling) is presented. The analysis of structural strength using ANSYS software is carried out. The rode type finite element model of the frame is presented. The directions of application and values of the resulting loads are determined taking into account the overloads experienced by the pilot in collisions. The boundary conditions and the deformation pattern of the frame structure when applying the deforming forces to the front beam along the longitudinal axis of the car, outside the longitudinal axis of the car and on the lateral truss of the car frame are given. The engineering analysis data show a good coincidence of the modeling results with the experimental data.

Experimental study on monitoring the bolt group looseness in a clamping support structure model

In this article, bolt group looseness monitoring in a clamping support structure model, which is under environmental random excitation, is experimentally investigated. The bolt group has 12 bolts, providing an essential clamping force to fix cargo during transportation. Seven kinds of bolt group looseness degree developed gradually are simulated in experiment. From an economic point of view, vibration transducer of accelerometer is used for monitoring. Time series analysis of Auto-Regressive with eXogenous model with input known and Auto-Regressive–Auto-Regressive with eXogenous model with input unknown are constructed, and the statistical indices of the model residual error are defined as the damage characteristic parameter indicating the bolt group looseness degree. The experimental analysis shows the effectiveness of the proposed method in monitoring the bolt group looseness at early stage, while the variation of structural resonance frequency can only be used to monitor large bolt group looseness degree. The experimental analysis also shows that under a stationary, broadband random excitation, the Auto-Regressive–Auto-Regressive with eXogenous model has the same bolt group looseness monitoring capability with the Auto-Regressive with eXogenous model.

An application of Structural Health Monitoring system based on FBG sensors to offshore wind turbine support structure model

The paper presents an application of Structural Health Monitoring system based on Fibre Bragg Grating sensors dedicated to an offshore wind turbine support structure (tripod) model. The experimental investigation was performed in a water basin for the wind turbine model fixed to a turntable that allowed to change the angle between the tripod legs and a wave generator direction. During measurements the structure was excited by artificial waves and rotor blades rotating simulating effect of wind blowing with different strength. The excitation simulated environmental loading typical for offshore wind turbine. One of the tripod's upper braces contained a flange simulating artificial circumferential crack occurrence. For the structure under simulating environmental condition four damage indexes (relative and absolute) were developed that allowed to detect the damage and localise it with accuracy to the tripod's leg.

Structure assisted compressed sensing reconstruction of undersampled AFM images

The use of compressed sensing in atomic force microscopy (AFM) can potentially speed-up image acquisition, lower probe-specimen interaction, or enable super resolution imaging. The idea in compressed sensing for AFM is to spatially undersample the specimen, i.e. only acquire a small fraction of the full image of it, and then use advanced computational techniques to reconstruct the remaining part of the image whenever this is possible. Our initial experiments have shown that it is possible to leverage inherent structure in acquired AFM images to improve image reconstruction. Thus, we have studied structure in the discrete cosine transform coefficients of typical AFM images. Based on this study, we propose a generic support structure model that may be used to improve the quality of the reconstructed AFM images. Furthermore, we propose a modification to the established iterative thresholding reconstruction algorithms that enables the use of our proposed structure model in the reconstruction process. Through a large set of reconstructions, the general reconstruction capability improvement achievable using our structured model is shown both quantitatively and qualitatively. Specifically, our experiments show that our proposed algorithm improves over established iterative thresholding algorithms by being able to reconstruct AFM images to a comparable quality using fewer measurements or equivalently obtaining a more detailed reconstruction for a fixed number of measurements.

Frequency Domain Decomposition performed on the strain data obtained from the aluminium model of an offshore support structure

This paper presents an application of Fibre Bragg Grating (FBG) sensors for Structural Health Monitoring (SHM) of offshore wind energy support structure model. The analysed structure is a tripod equipped with 16 FBG sensors.From a wide variety of Operational Modal Analysis (OMA) methods Frequency Domain Decomposition (FDD) technique is used in this paper under assumption that the input loading is similar to a white noise excitation. The FDD method can be applied using different sets of sensors, i.e. the one which contains all FBG sensors and the other set of sensors localised only on a particular tripod's leg. The cases considered during investigation were as follows: damaged and undamaged scenarios, different support conditions. The damage was simulated as an dismantled flange on an upper brace in one of the tripod legs. First the model was fixed to an antishaker table and investigated in the air under impulse excitations. Next the tripod was submerged into water basin in order to check the quality of the measurement set-up in different environmental condition. In this case the model was excited by regular waves.

Analytical Discussion on Stochastic Hydrodynamic Modeling of Support Structure of HAWAII WTG Offshore Wind Turbine

Floating structure such as tension leg platform, semi-submersible and spar are widely used in field of oil exploration and renewable energy system. All of these structures have the base cylinder support structure which have effective rule in overall dynamic of response. So the accurate and reliable modeling is needed for optimum design and understanding the physical background of these systems. The aim of this article is an analytical discussion on stochastic modeling of floating cylinder based support structure but an applicable one. Due to this a mathematical mass-damper-spring system of a floating cylinder of HAWAII WTG offshore wind as an applicable and innovative system is adopted to model a coupled degrees using random vibration in analytical way. A fully develop spectrum is adopted to solve the stochastic spectrum analytically by a proper approximation. Some acceptable assumption is adopted. The simplified but analytical and innovative hydrodynamic analysis of this study not only will help researcher to concentrate more physically on hydrodynamic analysis of floating structures but also can be useful for any quick, simplified and closed form analysis of a complicated problem in offshore engineering.

Comparison of different approaches to load calculation for the OWEC Quattropod jacket support structure

Accurate load simulations are necessary in order to design cost-efficient support structures for offshore wind turbines. Due to software limitations and confidentiality issues, support structures are often designed with sequential analyses, where simplified wind turbine and support structure models replace more detailed models. The differences with an integrated analysis are studied here for a commercial OWEC Quattropod. Integrated analysis seems to generally predict less damage than sequential analysis, decreasing by 30-70 percent in two power production cases with small waves.Additionally it was found that using a different realization of the wave forces for the retrieval run in sequential analysis leads to an increase of predicted damage, which can be explained as the effect of applying two independent wave force series at the same time.The midsection of the detailed support structure model used shell elements. Additional analyses for a model with an equivalent beam model of the midsection showed only small differences, mostly overpredicting damage by a few percent. Such models can therefore be used for relatively accurate analysis, if carefully calibrated.

Minimization of vibration power transmission from rotating machinery to a flexible supporting plate

This paper deals with the problem of optimum design of a foundation for rotating machinery with a view to minimize vibration transmission from a machine source to its supporting structure. The problem of analysis and optimization of the installation systems of machinery has been extensively researched on the assumption of a rigid supporting structure. The design based on a rigid supporting structure model is reasonable for the installation of machinery in many real engineering situations. However, this rigid support based model may not be appropriate for the problem studied herein where the machinery is to be installed on a relatively flexible supporting plate. Thus, a generalized mathematical model of mobility power flow is developed in this paper, with a rotating machine as vibration source, resilient mounts as isolator, and a flexible supporting plate as receiver. The objective of minimizing vibration transmission is realized by optimization of stiffness coefficients of resilient mounts with a constraint on the vibration level of the machine. The design objective is chosen as the minimization of the power flow transmitted to the flexible supporting plate through the resilient mounts at the excitation frequency of the machinery. Both a single excitation frequency and a range of excitation frequencies are considered. A gradient-based mathematical programing method is selected for its advantage of efficiently solving the current type of optimization problem with multiple mounts and multi-degree-of-freedom vibration transmission. The sensitivities of the objective and the constraint functions with respect to the design variables are derived analytically. The design and performance of the optimized machinery foundation is illustrated and discussed using several numerical examples. The optimized mounting system is suitable for the installation case of a rotating machine with a low or medium service speed on a flexible supporting plate structure.

Modeling and Performance Study of a Novel Cross-Node Support Structure of Free-Free Beam Vibration Gyroscope

Analyzing performance of the free-free beam vibration, a novel cross-node support structure of free-free beam vibration gyroscope (CNSG) is proposed. In this paper, CNSG mathematical model has been established and dynamics equation has been deduced. To compare performance of two-node support structure of free-free beam vibration gyroscope (TNSG) through ANSYS software and relative theoretical calculation. The result indicates that CNSG’s sensitivity has reduced by 10.738%, but shock resistance has increase by 94.44%, interference resistance frequency has increase by 66.02% and the cross-coupling error between the drive surface and the sensitive surface has reduced by 12.759%. Thus it gives a rational design of the support structure and provides a guideline on CNSG in complex application environment.