Temperature (T) is probably the most fundamental parameter in all kinds of science. Respective sensors are widely used in daily life. Besides conventional thermometers, optical sensors are considered to be attractive alternatives for sensing and on-line monitoring of T. This Review article focuses on all kinds of luminescent probes and sensors for measurement of T, and summarizes the recent progress in their design and application formats. The introduction covers the importance of optical probes for T, the origin of their T-dependent spectra, and the various detection modes. This is followed by a survey on (a) molecular probes, (b) nanomaterials, and (c) bulk materials for sensing T. This section will be completed by a discussion of (d) polymeric matrices for immobilizing T-sensitive probes and (e) an overview of the various application formats of T-sensors. The review ends with a discussion on the prospects, challenges, and new directions in the design of optical T-sensitive probes and sensors.

Luminescent probes and sensors for temperature.

Simple aerodynamic configurations under even modest conditions can exhibit complex flows with a wide range of temporal and spatial features. It has become common practice in the analysis of these flows to look for and extract physically important features, or modes, as a first step in the analysis. This step typically starts with a modal decomposition of an experimental or numerical dataset of the flowfield, or of an operator relevant to the system. We describe herein some of the dominant techniques for accomplishing these modal decompositions and analyses that have seen a surge of activity in recent decades [1–8]. For a nonexpert, keeping track of recent developments can be daunting, and the intent of this document is to provide an introduction to modal analysis that is accessible to the larger fluid dynamics community. In particular, we present a brief overview of several of the well-established techniques and clearly lay the framework of these methods using familiar linear algebra. The modal analysis techniques covered in this paper include the proper orthogonal decomposition (POD), balanced proper orthogonal decomposition (balanced POD), dynamic mode decomposition (DMD), Koopman analysis, global linear stability analysis, and resolvent analysis.

https://arc.aiaa.org/doi/pdf/10.2514/1.J056060

Modal Analysis of Fluid Flows: An Overview

Actuators are transducers that convert an electrical signal to a desired physical quantity. Active flow control actuators modify a flow by providing an electronically controllable disturbance. The field of active flow control has witnessed explosive growth in the variety of actuators, which is a testament to both the importance and challenges associated with actuator design. This review provides a framework for the discussion of actuator specifications, characteristics, selection, design, and classification for aeronautical applications. Actuator fundamentals are discussed, and various popular actuator types used in low-to-moderate speed flows are then described, including fluidic, moving object/surface, and plasma actuators. We attempt to highlight the strengths and inevitable drawbacks of each and highlight potential future research directions.

Actuators for Active Flow Control

This paper presents the results of a parametric experimental investigation aimed at optimizing the body force produced by single dielectric barrier discharge plasma actuators used for aerodynamic flow control. A primary goal of the study is the improvement of actuator authority for flow control applications at higher Reynolds number than previously possible. The study examines the effects of dielectric material and thickness, applied voltage amplitude and frequency, voltage waveform, exposed electrode geometry, covered electrode width, and multiple actuator arrays. The metric used to evaluate the performance of the actuator in each case is the measured actuator-induced thrust which is proportional to the total body force. It is demonstrated that actuators constructed with thick dielectric material of low dielectric constant produce a body force that is an order of magnitude larger than that obtained by the Kapton-based actuators used in many previous plasma flow control studies. These actuators allow operation at much higher applied voltages without the formation of discrete streamers which lead to body force saturation.

Optimization of Dielectric Barrier Discharge Plasma Actuators for Active Aerodynamic Flow Control

The current paper describes the development of pressure-sensitive paint (PSP) technology as an advanced measurement technique for unsteady flow fields and short-duration wind tunnels. Newly developed paint formulations have step response times approaching 1 μs, making them suitable for a wide range of unsteady testing. Developments in binder technology are discussed, which have resulted in new binder formulations such as anodized aluminium, thin-layer chromatography plate, polymer/ceramic, and poly(TMSP) PSP. The current paper also details modeling work done to describe the gas diffusion properties within the paint binder and understand the limitations of the paint response characteristics. Various dynamic calibration techniques for PSP are discussed, along with summaries of typical response times. A review of unsteady and high-speed PSP applications is presented, including experiments with shock tubes, hypersonic tunnels, unsteady delta wing aerodynamics, fluidic oscillator flows, Hartmann tube o...

https://journals.sagepub.com/doi/pdf/10.1243/09544100JAERO243

A review of pressure-sensitive paint for high-speed and unsteady aerodynamics

Range and Endurance Estimation for Low-Re Electric UAS

The current work focuses on the development and application of fast-responding polymer/ceramic pressure-sensitive paint (PSP) as an advanced surface pressure measurement technique for unsteady flow fields in large-scale wind tunnels. Three different experimental methods for acquiring quality PSP data are discussed: phase-averaging, realtime data acquisition using a high-speed camera, and single-shot lifetime. The three techniques are all demonstrated on a benchmark test case, resolving the unsteady surface pressure distribution on a hemispherical dome tested in the United States Air Force Research Laboratory’s Trisonic Gasdynamics Facility. The hemispherical dome was tested at a freestream Mach number of 0.6 with a total pressure of 1500 psf, where the Reynolds number was 2.4x10. At this flow condition, a predominant shear layer oscillated at 400 Hz over the test model, causing pressure fluctuations on the aft portion of the model. An assessment of the three techniques is presented, with the strengths and disadvantages for each technique evaluated through example.

Comparison of Unsteady Pressure-Sensitive Paint Measurement Techniques

Unmanned Aerial System Framework for Human-Robot Interaction

This paper describes the first-phase work of a comprehensive study on vortex dynamics during parallel blade-vortex interaction (BVI). Study of the vortex behavior sheds light on the fundamental interaction mechanism of BVI, and provides important validation data for computational investigations. Evidence has been found in previous studies that the vortex behavior during BVI varies with Reynolds number, but the effects are not clear. In the current study, the relation between Reynolds number and vortex behavior was investigated extensively. The influence of other factors on vortex behavior, such as vortex strength, is also discussed. A pneumatic vortex generation system has been built, which is capable of producing vortices with good repeatability in location, size and strength. The experiment is performed in a low speed wind tunnel usinga planar particle image velocimetry (PIV) technique to characterize the vortex and record BVI incidence. Results indicate that the vortex behavior during BVI strongly depends on the separation distance (h/c) between the vortex and the airfoil. A decrease in vortex strength during BVI is generally observed for h/c< 0.3. The PIV results also reveal the relation between Reynolds number and the vortex strength variation during the interaction.

http://absimage.aps.org/image/DFD13/MWS_DFD13-2013-001693.pdf

James W. Gregory

Papers

Range and Endurance Estimation for Low-Re Electric UAS

Comparison of Unsteady Pressure-Sensitive Paint Measurement Techniques

Unmanned Aerial System Framework for Human-Robot Interaction

Experimental Study of Vortex Dynamics during Blade-Vortex Interactions

Identification of Lagrangian Coherent Structures using the Background-Oriented Schlieren Method