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  • Supplementary Information Files for 'Design and validation of a nonlinear vibration absorber to attenuate torsional oscillations of propulsion systems' Abstract:Recent developments in propulsion systems to improve energy efficiency and reduce hazardous emissions often lead to severe torsional oscillations and aggravated noise. Vibration absorbers are typically employed to palliate the untoward effects of powertrain oscillations, with nonetheless an adverse impact on cost and constrained efficacy over a limited frequency range. Recently, the authors proposed the use of nonlinear vibration absorbers to achieve more broadband drivetrain vibration attenuation with low complexity and cost. These lightweight attachments follow the concept of targeted energy transfer, whereby vibration energy is taken off from a primary system without tuning requirements. In this paper, the design and experimental investigation of a prototype absorber is presented. The absorber is installed on a drivetrain experimental rig driven by an electric motor through a universal joint connection placed at an angle, thus inducing second order torsional oscillations. Vibration time histories with and without the absorber acting are recorded and compared. Frequency-energy plots are superimposed to the system nonlinear normal modes to verify the previously developed design methodology, whereas the achieved vibration reduction is quantified by comparing the acceleration amplitudes of the primary system and monitoring the distribution of energy damped in the primary system and the absorber. The absorber prototype was found to lead to significant vibration reduction away from resonance and near resonance with the additional feature of activation over a relatively broad frequency range.
    Data Types:
    • Image
  • Supplementary Information Files for 'Design and validation of a nonlinear vibration absorber to attenuate torsional oscillations of propulsion systems' Abstract:Recent developments in propulsion systems to improve energy efficiency and reduce hazardous emissions often lead to severe torsional oscillations and aggravated noise. Vibration absorbers are typically employed to palliate the untoward effects of powertrain oscillations, with nonetheless an adverse impact on cost and constrained efficacy over a limited frequency range. Recently, the authors proposed the use of nonlinear vibration absorbers to achieve more broadband drivetrain vibration attenuation with low complexity and cost. These lightweight attachments follow the concept of targeted energy transfer, whereby vibration energy is taken off from a primary system without tuning requirements. In this paper, the design and experimental investigation of a prototype absorber is presented. The absorber is installed on a drivetrain experimental rig driven by an electric motor through a universal joint connection placed at an angle, thus inducing second order torsional oscillations. Vibration time histories with and without the absorber acting are recorded and compared. Frequency-energy plots are superimposed to the system nonlinear normal modes to verify the previously developed design methodology, whereas the achieved vibration reduction is quantified by comparing the acceleration amplitudes of the primary system and monitoring the distribution of energy damped in the primary system and the absorber. The absorber prototype was found to lead to significant vibration reduction away from resonance and near resonance with the additional feature of activation over a relatively broad frequency range.
    Data Types:
    • Image
  • Supplementary information files for article: 'Simple and ultrafast resonance frequency and dissipation shift measurements using a fixed frequency drive'. A new method for determination of resonance frequency and dissipation of a mechanical oscillator is presented. Analytical expressions derived using the Butterworth-Van Dyke equivalent electrical circuit allow the determination of resonance frequency and dissipation directly from each impedance datapoint acquired at a fixed amplitude and frequency of drive, with no need for numerical fitting or measurement dead time unlike the conventional impedance or ring-down analysis methods. This enables an ultrahigh time resolution and superior noise performance with relatively simple instrumentation. Quantitative validations were carried out successfully against the impedance analysis method for inertial and viscous loading experiments on a 14.3 MHz quartz crystal resonator (QCR). Resonance frequency shifts associated with the transient processes of quick needle touches on a thiol self-assembled-monolayer functionalised QCR in liquid were measured with a time resolution of 112 μs, which is nearly two orders of magnitude better than the fastest reported quartz crystal microbalance. This simple and fast fixed frequency drive (FFD) based method for determination of resonance frequency and dissipation is potentially more easily multiplexable and implementable on a single silicon chip delivering economies of scale.
    Data Types:
    • Dataset
  • Supplementary information files for article: 'Simple and ultrafast resonance frequency and dissipation shift measurements using a fixed frequency drive'. A new method for determination of resonance frequency and dissipation of a mechanical oscillator is presented. Analytical expressions derived using the Butterworth-Van Dyke equivalent electrical circuit allow the determination of resonance frequency and dissipation directly from each impedance datapoint acquired at a fixed amplitude and frequency of drive, with no need for numerical fitting or measurement dead time unlike the conventional impedance or ring-down analysis methods. This enables an ultrahigh time resolution and superior noise performance with relatively simple instrumentation. Quantitative validations were carried out successfully against the impedance analysis method for inertial and viscous loading experiments on a 14.3 MHz quartz crystal resonator (QCR). Resonance frequency shifts associated with the transient processes of quick needle touches on a thiol self-assembled-monolayer functionalised QCR in liquid were measured with a time resolution of 112 μs, which is nearly two orders of magnitude better than the fastest reported quartz crystal microbalance. This simple and fast fixed frequency drive (FFD) based method for determination of resonance frequency and dissipation is potentially more easily multiplexable and implementable on a single silicon chip delivering economies of scale.
    Data Types:
    • Dataset
  • The combination of High-order methods and Large-Eddy Simulation (LES) is an ongoing research focus in turbulence due to the attractive dissipation characteristics of high-order methods. Whilst numerically speaking these methodologies are advantageous, their application is inhibited on industrial cases due to the inherent geometric complexities of such problems. Spectral/hp Element (SEM) solvers such as Nektar++, have potential to be bridge the gap between high-order methods and industrial geometric complexity. This study focuses on the intersection of the application of the SEM solver Nektar++ to an automotive geometry as well as the presentation of high-order mean flow characteristics for the SAE Notchback body. Using a 5th order polynomial expansion at ReL = 2.3 × 106 on a curvilinear grid, results are compared with those empirically achieved in other works. Implicit Sub-Grid scale modelling along with a novel Spectral-Vanishing Viscosity (SVV) approach is employed acting as an artificial diffusion operator preventing high-frequency instabilities and spurious oscillations. Suitable qualitative agreement between PIV and CFD methods is obtained, and quantitative agreement is demonstrated on CD with 9% difference. More extensive backlight separation and subsequent bootlid impingement is observed in CFD than presented in the literature. This might be caused due to differing inflow characteristics, resulting in CM and CL variance to experimental values. Along with the mean flow field characteristics, the methodology and the pipeline used to achieve such results and agreement is presented. The use of a wall-conforming unstructured curvilinear grid allows for significantly greater geometric flexibility whilst retaining the advantages of the high-order polynomial expansion.
    Data Types:
    • Other
  • The combination of High-order methods and Large-Eddy Simulation (LES) is an ongoing research focus in turbulence due to the attractive dissipation characteristics of high-order methods. Whilst numerically speaking these methodologies are advantageous, their application is inhibited on industrial cases due to the inherent geometric complexities of such problems. Spectral/hp Element (SEM) solvers such as Nektar++, have potential to be bridge the gap between high-order methods and industrial geometric complexity. This study focuses on the intersection of the application of the SEM solver Nektar++ to an automotive geometry as well as the presentation of high-order mean flow characteristics for the SAE Notchback body. Using a 5th order polynomial expansion at ReL = 2.3 × 106 on a curvilinear grid, results are compared with those empirically achieved in other works. Implicit Sub-Grid scale modelling along with a novel Spectral-Vanishing Viscosity (SVV) approach is employed acting as an artificial diffusion operator preventing high-frequency instabilities and spurious oscillations. Suitable qualitative agreement between PIV and CFD methods is obtained, and quantitative agreement is demonstrated on CD with 9% difference. More extensive backlight separation and subsequent bootlid impingement is observed in CFD than presented in the literature. This might be caused due to differing inflow characteristics, resulting in CM and CL variance to experimental values. Along with the mean flow field characteristics, the methodology and the pipeline used to achieve such results and agreement is presented. The use of a wall-conforming unstructured curvilinear grid allows for significantly greater geometric flexibility whilst retaining the advantages of the high-order polynomial expansion.
    Data Types:
    • Other
  • The heat transfer performance of a 5 mm internal diameter (I.D.) mesoscale continuous oscillatory flow crystalliser with smooth periodic constrictions (herein called SPC meso-tube) is herein reported for the first time for both steady flow and unsteady oscillatory flow conditions. Experimental values of the tube-side Nusselt number, Nut, accompanied by an estimability analysis, emphasised the key role played by smooth constrictions and bulk flow velocity in controlling tube-side heat transfer in the SPC meso-tube, while revealing a weaker influence of oscillatory flow on heat transfer enhancement in the tube. Although the presence of smooth constrictions provided an increased surface area to volume ratio, and re-circulation zones which promoted heat transfer rates, a maximum 1.7-fold heat transfer augmentation was obtained when fluid oscillations were combined with smooth constrictions. The behaviour of the SPC meso-tube was such that increasing the net flow Reynolds number, Reo, from 11 up to 54 with the combination of smooth constrictions and oscillatory flow resulted in the attainment of higher rates of heat transfer up to a maximum of 3.09. The Strouhal number, St, was also found to have a more significant effect on the heat transfer performance than oscillatory frequency. An empirical correlation was for the first time developed to describe the heat transfer characteristics of the SPC meso-tube, and predict based on experimental data for the range of net flow and oscillatory flow conditions investigated. A parameter estimability approach was also implemented to enhance the prediction capability of the correlation. The approach was based on a sequential orthogonalisation, thanks to which the most influential factors affecting the tube-side heat transfer were identified given the available experimental data. Overall, the results accentuate the efficient heat transfer capabilities of the SPC meso-tube in low laminar flow regimes, and its suitability for performing cooling crystallisations where tight temperature control of supersaturation is essential.
    Data Types:
    • Dataset
  • The heat transfer performance of a 5 mm internal diameter (I.D.) mesoscale continuous oscillatory flow crystalliser with smooth periodic constrictions (herein called SPC meso-tube) is herein reported for the first time for both steady flow and unsteady oscillatory flow conditions. Experimental values of the tube-side Nusselt number, Nut, accompanied by an estimability analysis, emphasised the key role played by smooth constrictions and bulk flow velocity in controlling tube-side heat transfer in the SPC meso-tube, while revealing a weaker influence of oscillatory flow on heat transfer enhancement in the tube. Although the presence of smooth constrictions provided an increased surface area to volume ratio, and re-circulation zones which promoted heat transfer rates, a maximum 1.7-fold heat transfer augmentation was obtained when fluid oscillations were combined with smooth constrictions. The behaviour of the SPC meso-tube was such that increasing the net flow Reynolds number, Reo, from 11 up to 54 with the combination of smooth constrictions and oscillatory flow resulted in the attainment of higher rates of heat transfer up to a maximum of 3.09. The Strouhal number, St, was also found to have a more significant effect on the heat transfer performance than oscillatory frequency. An empirical correlation was for the first time developed to describe the heat transfer characteristics of the SPC meso-tube, and predict based on experimental data for the range of net flow and oscillatory flow conditions investigated. A parameter estimability approach was also implemented to enhance the prediction capability of the correlation. The approach was based on a sequential orthogonalisation, thanks to which the most influential factors affecting the tube-side heat transfer were identified given the available experimental data. Overall, the results accentuate the efficient heat transfer capabilities of the SPC meso-tube in low laminar flow regimes, and its suitability for performing cooling crystallisations where tight temperature control of supersaturation is essential.
    Data Types:
    • Dataset