How well are hazards associated with derechos reproduced in regional climate simulations?

An 11-member ensemble of convection-permitting regional simulations of the fast-moving and destructive derecho of June 29 – 30, 2012 that impacted the northeastern urban corridor of the US is presented. This event generated 1100 reports of damaging winds, significant wind gusts over an extensive area of up to 500,000 km2, caused several fatalities and resulted in widespread loss of electrical power. Extreme events such as this are increasingly being used within pseudo-global warming experiments that seek to examine the sensitivity of historical, societally-important events to global climate non-stationarity and how they may evolve as a result of changing thermodynamic and dynamic context. As such it is important to examine the fidelity with which such events are described in hindcast experiments. The regional simulations presented herein are performed using the Weather Research and Forecasting (WRF) model. The resulting ensemble is used to explore simulation fidelity relative to observations for wind gust magnitudes, spatial scales of convection (as manifest in high composite reflectivity), and both rainfall and hail production as a function of model configuration (microphysics parameterization, lateral boundary conditions (LBC), start date, and use of nudging). We also examine the degree to which each ensemble member differs with respect to key mesoscale drivers of convective systems (e.g. convective available potential energy and vertical wind shear) and critical manifestations of deep convection; e.g. vertical velocities, cold pool generation, and how those properties relate to correct characterization of the associated atmospheric hazards (wind gusts and hail). Here, we show that the use of a double-moment, 7-class scheme with number concentrations for all species (including hail and graupel) results in the greatest fidelity of model simulated wind gusts and convective structure against the observations of this event. We further show very high sensitivity to the LBC employed and specifically that simulation fidelity is higher for simulations nested within ERA-Interim than ERA5.

Assessing the contribution of active somatosensory stimulation to self-acceleration perception in dynamic driving simulators

In dynamic driving simulators, the experience of operating a vehicle is reproduced by combining visual stimuli generated by graphical rendering with inertial stimuli generated by platform motion. Due to inherent limitations of the platform workspace, inertial stimulation is subject to shortcomings in the form of missing cues, false cues, and/or scaling errors, which negatively affect simulation fidelity. In the present study, we aim at quantifying the relative contribution of an active somatosensory stimulation to the perceived intensity of self-motion, relative to other sensory systems. Participants judged the intensity of longitudinal and lateral driving maneuvers in a dynamic driving simulator in passive driving conditions, with and without additional active somatosensory stimulation, as provided by an Active Seat (AS) and Active Belts (AB) integrated system (ASB). The results show that ASB enhances the perceived intensity of sustained decelerations, and increases the precision of acceleration perception overall. Our findings are consistent with models of perception, and indicate that active somatosensory stimulation can indeed be used to improve simulation fidelity.

Dynamic Simulation of Space Debris Cloud Capture Using the Tethered Net

Space debris, especially the space debris cloud, has threatened severely the safety of future space missions. In the framework of multibody system dynamics, a computational approach is proposed in this study to investigate the dynamics of net deployment and capture of space debris cloud using this net subject to large overall motions and large deformations. To obtain high simulation fidelity of capturing space debris cloud, the gradient deficient beam element of the absolute nodal coordinate formulation (ANCF) is employed to discretize threads which are woven into the net. The normal contact force between the net and the debris cloud and among debris particles is computed by using the penalty method. Some deployment examples are presented to investigate the influences of shooting velocity of bullets and microgravity as well as the angle between the traveling direction of the net and the microgravity direction on the deployment characteristics of the tethered net. Other capturing examples are given to clarify the effect of the deployment area of the net at the moment it starts to contact with the debris cloud on the capture rate and to demonstrate the effectiveness of the proposed approach for capturing space debris cloud using the net in microgravity conditions.

Development and Validation of Multiscale Coupled Thermal-Hydraulic Code Combining RELAP5 and Fluent Code

In nuclear reactor system research, the multiscale coupled thermal-hydraulic (T-H) system code and CFD code is one of the most prevalent research areas, and it could help improve simulation fidelity and optimize nuclear reactor design. Additionally, a new idea known as the function fitting method (FFM) for coupling parameter distribution has been newly proposed for exchanging data on the coupling interface, which uses math equations to present the velocity distribution characteristics at the coupling interface. This method could improve the simulation error and numerical instability. To verify and validate the abovementioned FFM, a comparison between the velocity function shape by FFM and real velocity distribution was completed. Besides, the Edwards pipe blowdown test results were used to verify the coupled code. The results showed good agreement with experiment results, and a better simulation accuracy compared to previous work. The current work will establish the ability to explore multiscale coupled thermal-hydraulic operation characteristics which permit precise local parameter distribution.

Effects of Simulation Fidelity on Learning Transfer

This paper examines, via literature review, the relationship between simulation fidelity and transfer of learning to the operational environment. This paper focuses on the application of simulation to medical, maritime and aviation training. The literature showed that, contrary to intuition, novice learners derived little benefit from high-fidelity simulation. There were even some indications that high-fidelity simulation could impair transfer for novice learners. The literature showed that expert, or near expert, learners required high-fidelity simulation for effective transfer. The literature also showed strong evidence that cognitive skill transfer required high levels of cognitive fidelity, but was mostly unrelated to physical and functional fidelity. There was little information regarding the link between psychomotor and procedural skill transfer and cognitive fidelity. Keywords: Simulation, fidelity, learning transfer, skill transfer

An Approximate Finite State Dynamic Wake Model for Predictions of Inflow below the Rotor

The velocity potential based finite state dynamic inflow model can predict inflow anywhere in the flow field once velocity potential states and costates are known. However, solution to costate equations requires backward time marching, making it incompatible for integration into real-time flight simulation. This paper explores two types of quasi-steady approximations to the costate equations, both of which eliminate the need for backward time marching. The fidelities of the resulting inflow models are assessed through comparisons of off-disk inflow predictions for an isolated rotor. Further, the implication of the inflow model approximations on the flight simulation fidelity is assessed using the coupled body/rotor/inflow dynamics model of a generic helicopter model. It is shown that, in both cases, the quasi-steady approximations to the inflow model retain simulation model fidelity at low frequencies, a typical frequency range of pilot control inputs. Notable fidelity loss is seen at high-frequency control inputs, specifically for cases where horizontal tail is operating at a higher dynamic pressure within the rotor wake.

The Potential of a Multi-Fidelity Approach to Gas Turbine Combustor Design Optimization

The desire to reduce gas turbine emissions drives the use of design optimization approaches within the combustor design process. However, the relative cost of combustion simulations can prohibit such optimizations from being carried out within an industrial setting. Strategies which can significantly reduce the cost of such studies can enable designers to further improve emissions performance. The following paper investigates the application of a multi-fidelity surrogate modelling approach to the design optimization of a typical gas turbine combustor from a civil airliner engine. Results over three different case studies of varying problem dimensionality indicate that a multi-fidelity surrogate modelling based design optimization, whereby the simulation fidelity is varied by adjusting the coarseness of the mesh, can indeed improve optimization performance. These results indicate that such an approach has the potential to significantly reduce design optimization cost whilst achieving similar, or in some cases superior, design performance.

Effectiveness of technology-enhanced simulation in teaching digital rectal examination: a systematic review narrative synthesis

BackgroundDigital rectal examination (DRE) is a challenging examination to learn.ObjectiveTo synthesise evidence regarding the effectiveness of technology-enhanced simulation (TES) for acquiring DRE skills.Study selectionEMBASE, Medline, CINAHL, Cochrane, Web of Knowledge (Science and Social Science), Scopus and IEEE Xplore were searched; the last search was performed on 3 April 2019. Included were original research studies evaluating TES to teach DRE. Data were abstracted on methodological quality, participants, instructional design and outcomes; a descriptive synthesis was performed. Quality was assessed using a modified Medical Education Research Study Quality Instrument. The study design domain was modified by scoring the papers based on (1) evaluation of risk of bias for randomised controlled trials, (2) description of participants and (3) assessment of robustness and degree of simulation fidelity of the assessments used to evaluate learning.Findings863 articles were screened; 12 were eligible, enrolling 1507 prequalified medical/clinical students and 20 qualified doctors. For skill acquisition, role player was statistically significantly superior to a static manikin (2 studies). For knowledge acquisition, manikin use was significantly superior to role player (1 study); 2 studies showed no difference. For confidence, manikin use was significantly superior to no manikin (4 studies). For comfort, manikin use was significantly superior to no manikin (2 studies). For anxiety, role player was significantly superior to manikin (1 study).Median overall quality score (QS) was 48% (27–62). Highest median QS was 73% (33–80) for data analysis; lowest median QS was 20% (7–40) for the validity of instrument. Six papers scored over 50% of the maximum score for overall quality.ConclusionsTES training is associated with improved DRE skills and should be used more widely.