Estimating Inducer Blade Damping in Water with On-Blade Strain Measurements

This paper describes the testing, methodology, and results for estimating critical damping ratios of inducer blade structural natural frequencies. A sub-scale inducer water flow test was performed with on-blade strain gauge measurements. Data were acquired in quiescent air and water, and also at several shaft speeds and operating conditions. Two methods were used to provide active excitation to the blades. The first was to impart a mechanical impulse to the inducer shaft and observe the strain gauge response. The second was to install a stator plate upstream of the inducer to create a non-uniform but regular pressure field at the inducer inlet. There are challenges with using either approach, but damping information was extracted using both methods. Results showed that the critical damping ratio for a given blade mode increased from air to quiescent water, and also increased when the inducer was spinning

Single Degree-of-Freedom Modeling of SLS Liquid Hydrogen Pre-Valve Flow Guide to Enable Rapid Transient Analysis

A unique single degree-of-freedom approximation technique has been developed to enable rapid application of a temporally-defined multi-spectral semi-narrow-band loading for generation of realistic stress/cycle values compared to a resonant analysis. The technique uses the harmonic analysis at resonance of a high-fidelity finite element model to produce a transfer function, which is then used to calibrate the response of the SDOF model. A standard numerical ordinary differential equation solver is then used to obtain the temporal response, and its histogram is used in a fatigue/fracture model. This technique is related to other SDOF methods used widely in industry, such as Miles' Equation and the Shock Response Spectra, but it is unique in that it produces a realistic time history of the response. The most obvious error in the process, which is the effect of closely-spaced modes, was also assessed using the parallel application of several SDOF models, and the error is shown to be small. The application of this unique and tractable reduced-order methodology has enabled the SLS program to avoid substantial cost and schedule penalties if a redesign or change of material were required. It has also enabled quick analysis of a number of other structures undergoing the same or similar excitation fields, and quick assessment when the excitation and structural configuration has been altered due to design changes in the system

Fluctuating Pressure Environments and Hydrodynamic Radial Force Mitigation for a Two Blade Unshrouded Inducer

Fluctuating pressure data from water flow testing of an unshrouded two blade inducer revealed a cavitation induced oscillation with the potential to induce a radial load on the turbopump shaft in addition to other more traditionally analyzed radial loads. Subsequent water flow testing of the inducer with a rotating force measurement system confirmed that the cavitation induced oscillation did impart a radial load to the inducer. After quantifying the load in a baseline configuration, two inducer shroud treatments were selected and tested to reduce the cavitation induced load. The first treatment was to increase the tip clearance, and the second was to introduce a circumferential groove near the inducer leading edge. Increasing the clearance resulted in a small load decrease along with some steady performance degradation. The groove greatly reduced the hydrodynamic load with little to no steady performance loss. The groove did however generate some new, relatively high frequency, spatially complex oscillations to the environment

Rotating Balances Used for Fluid Pump Testing

Marshall Space Flight Center has developed and demonstrated two direct read force and moment balances for sensing and resolving the hydrodynamic loads on rotating fluid machinery. These rotating balances consist of a series of stainless steel flexures instrumented with semiconductor type, unidirectional strain gauges arranged into six bridges, then sealed and waterproofed, for use fully submerged in degassed water at rotational speeds up to six thousand revolutions per minute. The balances are used to measure the forces and moments due to the onset and presence of cavitation or other hydrodynamic phenomena on subscale replicas of rocket engine turbomachinery, principally axial pumps (inducers) designed specifically to operate in a cavitating environment. The balances are inserted into the drive assembly with power to and signal from the sensors routed through the drive shaft and out through an air-cooled twenty-channel slip ring. High frequency data - balance forces and moments as well as extensive, flush-mounted pressures around the rotating component periphery - are acquired via a high-speed analog to digital data acquisition system while the test rig conditions are varied continuously. The data acquisition and correction process is described, including the in-situ verifications that are performed to quantify and correct for known system effects such as mechanical imbalance, "added mass," buoyancy, mechanical resonance, and electrical bias. Examples of four types of cavitation oscillations for two typical inducers are described in the laboratory (pressure) and rotating (force) frames: 1) attached, symmetric cavitation, 2) rotating cavitation, 3) attached, asymmetric cavitation, and 4) cavitation surge. Rotating and asymmetric cavitation generate a corresponding unbalanced radial force on the rotating assembly while cavitation surge generates an axial force. Attached, symmetric cavitation induces no measurable force. The frequency of the forces can be determined a priori from the pressure environment while the magnitude of the hydrodynamic force is proportional to the pressure unsteadiness

Estimating Inducer Blade Damping in Water with On-Blade Strain Measurements

No abstract availabl

Water Flow Testing and Unsteady Pressure Analysis of a Two-Bladed Liquid Oxidizer Pump Inducer

The unsteady fluid dynamic performance of a cavitating two-bladed oxidizer turbopump inducer was characterized through sub-scale water flow testing. While testing a novel inlet duct design that included a cavitation suppression groove, unusual high-frequency pressure oscillations were observed. With potential implications for inducer blade loads, these high-frequency components were analyzed extensively in order to understand their origins and impacts to blade loading. Water flow testing provides a technique to determine pump performance without the costs and hazards associated with handling cryogenic propellants. Water has a similar density and Reynolds number to liquid oxygen. In a 70%-scale water flow test, the inducer-only pump performance was evaluated. Over a range of flow rates, the pump inlet pressure was gradually reduced, causing the flow to cavitate near the pump inducer. A nominal, smooth inducer inlet was tested, followed by an inlet duct with a circumferential groove designed to suppress cavitation. A subsequent 52%-scale water flow test in another facility evaluated the combined inducer-impeller pump performance. With the nominal inlet design, the inducer showed traditional cavitation and surge characteristics. Significant bearing loads were created by large side loads on the inducer during synchronous cavitation. The grooved inlet successfully mitigated these loads by greatly reducing synchronous cavitation, however high-frequency pressure oscillations were observed over a range of frequencies. Analytical signal processing techniques showed these oscillations to be created by a rotating, multi-celled train of pressure pulses, and subsequent CFD analysis suggested that such pulses could be created by the interaction of rotating inducer blades with fluid trapped in a cavitation suppression groove. Despite their relatively low amplitude, these high-frequency pressure oscillations posed a design concern due to their sensitivity to flow conditions and test scale. The amplitude and frequency of oscillations varied considerably over the pump s operating space, making it difficult to predict blade loads

Providing Psychosocial support through Virtual Support Groups to Patients with Parkinson’s Disease and their Caregivers: A Scoping Review

Abstract Individuals with Parkinson’s disease (PD) may require substantial support, owing to the significant physical, cognitive, and psychological symptoms that are associated with the disease. Furthermore, caregivers of individuals with PD may struggle with the demands of their responsibilities, which can impact their quality of life and ability to participate in social activities. The purpose of this scoping review was to evaluate the factors associated with providing psychosocial support to individuals with PD and their caregivers through virtual support groups. We applied the scoping review methodology described by Arksey and O’Malley to the 15 articles identified within our literature search. Evidence suggests that virtual support groups provide similar experiences to in-person support groups, demonstrating that they can provide an effective form of support, particularly for individuals who have difficulty leaving their home (possibly due to symptom severity or mobility issues) or who are unable to locate suitable in-person resources in their geographical area. Thus, online support groups appear to serve as an effective form of social support for individuals with PD and their caregivers. The perceived level of benefit derived from online support groups is further influenced by factors such as age, group similarity, and disease severity. Overall, the use of virtual support groups may increase access to social support by addressing accessibility barriers and may be a particularly valuable adjunctive service for individuals living in rural areas, or for whom PD symptoms present mobility challenges

How IBD patients cope with IBD: A systematic review

AbstractObjectiveInflammatory bowel disease (IBD) can have a significant impact on psychological wellbeing and quality of life. How one responds to and copes with IBD may be an important determinant of psychological wellbeing. We aimed to systematically review all published literature regarding coping strategies of IBD patients.MethodsOvid and Pubmed databases were searched over 6months. All articles about coping strategies of IBD patients were included.ResultsThirty-nine articles using twenty-two survey instruments were found, of which twenty-six were adult exclusive, eleven were children exclusive, and two had both adults and children. Two were interventional, four were longitudinal, and the rest were cross-sectional studies. Four studies were qualitative while the rest used quantitative measures. Variance in research designs and coping instruments led to inconsistent results. The most common theme was that emotion-focused coping was associated with worse psychological outcomes, while the effect of problem-focused coping was less consistently associated with better psychological outcomes.ConclusionsMore longitudinal and interventional studies are needed to causally link coping strategies with psychological outcomes in IBD patient

Does Computerized Cognitive Behavioral Therapy Help People with Inflammatory Bowel Disease? : A Randomized Controlled Trial

BACKGROUND: Cognitive behavioral therapy may be useful for improving health-related quality of life (HRQOL) of at least some patients with inflammatory bowel disease (IBD), especially those with psychiatric comorbidities. However, cognitive behavioral therapy can be difficult to access. These difficulties can be overcome by computerized cognitive behavioral therapy (CCBT). This is a randomized controlled trial of a self-administered CCBT intervention for patients with IBD focused on improving HRQOL. It is hypothesized that CCBT completers will have an improved HRQOL relative to people not allocated to CCBT. METHODS: Patients with IBD were randomly allocated to CCBT (n = 113) versus treatment as usual (n = 86). The IBD Questionnaire at 12 weeks after baseline was the primary outcome, while generic HRQOL, anxiety, depression, coping strategies, perceived stress, and IBD symptoms were secondary outcomes. Outcomes were also measured at 6 months after baseline. Predictors of dropout were also determined. RESULTS: Twenty-nine CCBT participants (25.7%) completed the CCBT. The IBD Questionnaire was significantly increased at 12 weeks in CCBT completers compared with treatment-as-usual patients (F = 6.38, P = 0.01). Short Form-12 mental score (F = 5.00, P = 0.03) was also significantly better in CCBT compared with treatment-as-usual patients at 12 weeks. These outcomes were not maintained at 6 months. The predictors of dropout were baseline depression, biological use, lower IBD Questionnaire scores, and not having steroids. CONCLUSIONS: Improvements at 12 weeks after baseline were not maintained at 6 months. Future research should aim to improve adherence rates. Moreover, CCBT may not work for patients with IBD with comorbid depression

Vegetable Shipping Line Graph Testing Survey

Survey results from both an online and in-paper survey designed to determine if how uncertainty information was displayed changed users' decisions from and interpretations of the data. Participants for the survey were recruited in different ways to target different audiences