Browsing by Author "Green, Richard"

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    Air jet flow control on pitching aerofoils
    (Cranfield University, 2019-07-08 09:09) Prince, Simon; Green, Richard; Khodaglian, Vahik
    Experimental data on the effect of steady and pulsed air jet vortex generator blowing on a RAE9645 aerofoil section in dynamic stall.
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    ItemOpen Access
    The effect of steady and pulsed air jet vortex generator blowing on an aerofoil section model undergoing sinusoidal pitching
    (Vertical Flight Society, 2019-07-01) Prince, Simon A.; Green, Richard; Coton, Frank; Wang, Yaxing
    Experimental results are reported on the assessment of steady and pulsed air jet vortex generators (AJVGs) for the suppression of dynamic stall on a sinusoidal pitching RAE9645 airfoil model. Tests at Rec of 1 million, at reduced pitching frequencies between 0.01 and 0.10 were performed with and without steady and pulsed AJVG blowing. The effect of jet momentum coefficient (0.0003< C μ < 0.0046), jet duty cycle (0.25< DC< 1) and jet pulsing frequency (0.29< F +< 2.93) were investigated. Pulsed air jet blowing with F + in the range 0.5–1.0 and with a duty cycle in the range 0.4–0.5, was found to be the most effective to achieve full suppression of dynamic stall vortex formation.
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    Supporting operational decision making concerning aircraft structural integrity damage identified during maintenance.
    (2021-06-10) Green, Richard; McNaught, Ken R.; Saddington, Alistair J.
    Military aircraft operations balance delivery pressures and engineering risks. Aircraft structural damage incurred in-service creates complex risk decision problems for managers deliberating maintenance activity such as delaying rectification to continue operations, or grounding an aircraft or entire fleet. In many operational settings, aircraft availability demands restrict the time, information, or resources to analyse structural risks, making formal risk or decision analysis intractable. Exact solutions are information intensive and require specialist knowledge or machinery beyond the capabilities of generalist engineering managers, often compelling decision-makers to use their subjective judgement in an unsupported way. For actors deliberating aircraft maintenance structural risks in such circumstances, a novel approach based upon heuristics, argument and bounded rationality is proposed, which was informed by the results from a survey of engineering practitioners and case study analyses. Testing of the approach was carried-out with 21 aircraft engineering decision-makers with experience of structural integrity risks, split into three groups, using realistic but fictional textual simulations of aircraft maintenance. One group used existing decision justification approaches and were compared with a second group who provided decision justifications using the novel approach. Users of the novel approach felt supported and were very confident in their justifications. The third group of raters comparing the two sets of decision justifications indicated preferences using Likert scales against the criteria: which is easier to understand, which is more transparent, and which gives the better justification. Analysis of the comparative results using ANOVA provided evidence that the novel approach enabled better decision justification and transparency compared to existing approaches. The novel approach aids decision-makers compelled to use their unsupported subjective judgement, improving organisational resilience by improving robustness and stretching system process to handle surprises, and providing a clear record of the decision basis for post hoc review.