Lift Response of a Stalled Wing to Pulsatile Disturbances

The transient lift response of a low-Reynolds-number wing subjected to small amplitude pulsatile disturbances is investigated. The wing has a small aspect ratio and a semicircular planform, and it is fully stalled at a 20 deg angle of attack. Microvalve actuators distributed along the leading edge of the wing produce the transient disturbance. It is shown that the lift response to a single pulse increases with increasing actuator supply pressure and that the lift response curves are similar to each other when scaled by the total impulse. Furthermore, for fixed actuator supply pressure, the amplitude and total impulse of the transient lift response curve increases with increasing external flow speed. In this case, the lift response curves are similar when scaled by the dynamic pressure. The lift response to a single pulse can be treated as a filter kernel, and it can be used to predict the lift time history for the arbitrary actuator input signals. The kernel is similar in shape to transient measurements obtained by other investigators on two-dimensional wings and flaps. Comparisons between the model predictions and the experiments using multiple pulse inputs and square-wave modulated input signals at low frequencies are presented

Closed-Loop Control of a Wing in an Unsteady Flow

The lift response of the separated flow over a wing to different actuator input disturbances is used to obtain linear models useful for closed-loop control design. The wing has a small aspect ratio, a semi-circular planform, and is fully stalled at a 20° angle of attack. Individual pulse-like disturbances and step-input disturbances with randomized frequency were inputs to the actuator, and the lift coefficient increments were output signals. The "prediction error method" system identification technique was used to obtain two linear models of the separated flow. A 4th order model reproduced the non-minimum phase behavior of the pulse input, but did not work well for control purposes. The second model identified was limited to first order. The first order model proved to be useful for designing a proportional-integral feedback controller capable of suppressing lift oscillations in unsteady flows. Good suppression of lift oscillations was observed in the experiment after a step change in wind tunnel flow speed occurred. When the control system was tested with a randomized freestream velocity, it reduced the root-mean-square lift oscillation by 50 percent relative to the uncontrolled case

Low Reynolds Number Wing Response to an Oscillating Freestream With and Without Feed Forward Control

The unsteady lift of a low Reynolds number wing in an oscillating freestream is documented in terms of its amplitude and phase. The phase variation of the lift relative to the freestream velocity shows a larger phase difference than predicted by classical unsteady flow theory. A constant time delay between the lift and the actuator was observed to be τ^+ = t_(delay)U/c = 5.3 when normalized by the freestream speed and chord. Feed forward control of pulsed-jet actuators is used to modulate the lift coefficient of the wing, in an attempt to suppress the lift oscillations. Suppression of the fluctuating lift at the fundamental frequency was partially successful, but additional "noise" was added to harmonics of the lift signal by the controller

Strong Metal‐support Interactions in Photocatalysis: Fundamentals and Design Methods

International audienceAbstract Engineering the composition and geometry of metallic sites has become a popular manner to boost reaction rate and control reaction selectivity in heterogeneous catalysis. Many studies have been devoted to enhancing the stability of metallic nanoparticles during catalytic reactions by dispersion on metal oxide supports such as TiO 2 , CeO 2 or Nb 2 O 5 . These supports not only modulate electronic properties and dispersion/stabilization of metallic nanoparticle but also influence catalytic selectivity, resulting in the so‐called “strong metal‐support interaction” (SMSI). In this minireview, we outlined the discovery and fundamentals of SMSI, as well as its extensive development over years. In addition, we summarized recent approaches developed to induce the construction of SMSI between different metal nanoparticles and metal oxide supports. Associated characterization microscopic and spectroscopic techniques were emphasized. Despite being a prevalent concept in catalysis, the number of studies on SMSI in heterogeneous photocatalysis has been even in limitation. Herein, we highlighted the beneficial effects of SMSI on boosting photocatalytic activity for CO 2 reduction and H 2 evolution reactions. In general, despite some controversial aspects of the SMSI, this concept offers wide opportunities ahead and encourages researchers to rethink the local active site localization and photocatalyst design

Innovating Process Improvements in Manufacturing Operations (Semester Unknown) IPRO 304: InnovatingProcessImprovementsInManufacturingOperationsIPRO304MidTermPresentationSp09

The purpose of this IPRO is to develop a robust, working prototype that can automatically monitor and detect a problem with a milling machine at A. FInkl & Sons Co. This IPRO is in its fourth semester and there are two challenges remaining: (1) alerting management to the detection of broken teeth during machining; and (2) developing spatial representations of items undergoing heat treatment. However, A. Finkl & Sons has asked us to concentrate solely on the goal of finding a way to detect when a break occurs in one of the milling teeth and then alert the mechanic monitoring the machine in order to replace it. This system will involve measuring vibrations using an accelerometer or by the use of laser detection. The goal of this IPRO is to research, test, and inform A. FInkl & Sons of the best solution to invest in, therefore they can decide what is better for their company.Sponsorship: A. Finkl & Sons Co.Deliverable

Innovating Process Improvements in Manufacturing Operations (Semester Unknown) IPRO 304: InnovatingProcessImprovementsInManufacturingOperationsIPRO304ProjectPlanSp09

The purpose of this IPRO is to develop a robust, working prototype that can automatically monitor and detect a problem with a milling machine at A. FInkl & Sons Co. This IPRO is in its fourth semester and there are two challenges remaining: (1) alerting management to the detection of broken teeth during machining; and (2) developing spatial representations of items undergoing heat treatment. However, A. Finkl & Sons has asked us to concentrate solely on the goal of finding a way to detect when a break occurs in one of the milling teeth and then alert the mechanic monitoring the machine in order to replace it. This system will involve measuring vibrations using an accelerometer or by the use of laser detection. The goal of this IPRO is to research, test, and inform A. FInkl & Sons of the best solution to invest in, therefore they can decide what is better for their company.Sponsorship: A. Finkl & Sons Co.Deliverable

Innovating Process Improvements in Manufacturing Operations (Semester Unknown) IPRO 304: InnovatingProcessImprovementsInManufacturingOperationsIPRO304PosterSp09

The purpose of this IPRO is to develop a robust, working prototype that can automatically monitor and detect a problem with a milling machine at A. FInkl & Sons Co. This IPRO is in its fourth semester and there are two challenges remaining: (1) alerting management to the detection of broken teeth during machining; and (2) developing spatial representations of items undergoing heat treatment. However, A. Finkl & Sons has asked us to concentrate solely on the goal of finding a way to detect when a break occurs in one of the milling teeth and then alert the mechanic monitoring the machine in order to replace it. This system will involve measuring vibrations using an accelerometer or by the use of laser detection. The goal of this IPRO is to research, test, and inform A. FInkl & Sons of the best solution to invest in, therefore they can decide what is better for their company.Sponsorship: A. Finkl & Sons Co.Deliverable

Innovating Process Improvements in Manufacturing Operations (Semester Unknown) IPRO 304

The purpose of this IPRO is to develop a robust, working prototype that can automatically monitor and detect a problem with a milling machine at A. FInkl & Sons Co. This IPRO is in its fourth semester and there are two challenges remaining: (1) alerting management to the detection of broken teeth during machining; and (2) developing spatial representations of items undergoing heat treatment. However, A. Finkl & Sons has asked us to concentrate solely on the goal of finding a way to detect when a break occurs in one of the milling teeth and then alert the mechanic monitoring the machine in order to replace it. This system will involve measuring vibrations using an accelerometer or by the use of laser detection. The goal of this IPRO is to research, test, and inform A. FInkl & Sons of the best solution to invest in, therefore they can decide what is better for their company.Sponsorship: A. Finkl & Sons Co.Deliverable

Innovating Process Improvements in Manufacturing Operations (Semester Unknown) IPRO 304: InnovatingProcessImprovementsInManufacturingOperationsIPRO304BrochureSp09

The purpose of this IPRO is to develop a robust, working prototype that can automatically monitor and detect a problem with a milling machine at A. FInkl & Sons Co. This IPRO is in its fourth semester and there are two challenges remaining: (1) alerting management to the detection of broken teeth during machining; and (2) developing spatial representations of items undergoing heat treatment. However, A. Finkl & Sons has asked us to concentrate solely on the goal of finding a way to detect when a break occurs in one of the milling teeth and then alert the mechanic monitoring the machine in order to replace it. This system will involve measuring vibrations using an accelerometer or by the use of laser detection. The goal of this IPRO is to research, test, and inform A. FInkl & Sons of the best solution to invest in, therefore they can decide what is better for their company.Sponsorship: A. Finkl & Sons Co.Deliverable