Überprüfung der Homogenitätsannahme und der Gültigkeit der Taylor Hypothese in atmosphärischen Grenzschichtströmungen mittels räumlich verteilter Messungen einer UAS Flotte

2021 ◽  
Author(s):  
Josef Zink ◽  
Norman Wildmann ◽  
Tamino Wetz
Keyword(s):  
Unmanned Aerial System

<p>Im Rahmen des Projekts SWUF-3D wurden während der Messkampagne FESSTVaL im Sommer 2021 am Grenzschichtmessfeld (GM) Falkenberg des DWD räumlich separierte Messungen in der atmosphärischen Grenzschicht mittels einer Flotte Quadrotor UAS (Unmanned Aerial System) durchgeführt. Es wurden mehrere UAS in einer horizontalen Ebene sowohl in Strömungsrichtung, als auch senkrecht dazu angeordnet, um so das turbulente Windfeld simultan an mehreren festen Punkten zu vermessen. Die Strömungsrichtung wurde dabei aus Windmessungen des 99 m hohen Messmasts am GM bestimmt.  Variierende räumliche Abstände zwischen benachbarten UAS im horizontalen Messmuster erlauben Turbulenzauswertungen als Funktion der Distanz.  Die Messungen können genutzt werden, um die in der atmosphärischen Grenzschichtforschung vielfach verwendeten Annahmen der Homogenität und der Taylor Hypothese zu überprüfen.  Um mögliche Abhängigkeiten dieser Annahmen von unterschiedlichen atmosphärischen Randbedingungen zu erkennen, wurde die Messstrategie unter verschiedenen Bedingungen (neutral, konvektiv und stabil geschichtete Grenzschicht) wiederholt. Die Messergebnisse zeigen, dass im Rahmen der Messgenauigkeit keine signifikante Verletzung der Homogenitätsannahme für die untersuchten atmosphärischen Randbedingungen in der Mikroskala vorliegt.  Abnahmen mit der Distanz der in Strömungsrichtung berechneten Kreuzkorrelationsfunktionen und Kohärenzen, deuten darauf hin, dass Taylor’s Hypothese der eingefrorenen Turbulenz, die mit dem mittleren Wind transportiert wird, nicht gänzlich für alle Skalen anwendbar ist.  Jedoch sind hierbei auch Messgenauigkeiten der UAS und leichte Fehlausrichtung des Messmusters gegenüber der tatsächlich vorherrschenden Windrichtung während des Flugs zu berücksichtigen. Die Fehlausrichtung führt dazu, dass eine turbulente Struktur nicht parallel durch alle Messpunkte durchwandert, sondern mit einer seitlichen Verschiebung. Die Studie zeigt das Potential zur in-situ Vermessung zeitlich und räumlich komplexer Strömungen mit einer Flotte von Quadrotor UAS im Skalenbereich von 5 m bis 200 m. Eine Ausdehnung des Messvolumens über die Mikroskala hinaus kann in Zukunft einen wichtigen Beitrag zum besseren Verständnis kohärenter Strukturen in der turbulenten atmosphärischen Grenzschicht leisten.</p>

LIGHTER-THAN-AIR (LTA) UNMANNED AERIAL SYSTEM (UAS) CARRIER CONCEPT FOR SURVAILLANCE AND DISASTER MANAGEMENT

2019 ◽  
Vol 3 ◽  
pp. 1255
Author(s):  
Ahmad Salahuddin Mohd Harithuddin ◽  
Mohd Fazri Sedan ◽  
Syaril Azrad Md Ali ◽  
Shattri Mansor ◽  
Hamid Reza Jifroudi ◽  
...  
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Disaster Management ◽  
Unmanned Aerial Systems ◽  
Unmanned Aerial System ◽  
Border Control ◽  
Aerial Vehicles ◽  
Operational Safety ◽  
In Situ Methods ◽  
Aerial Systems

Unmanned aerial systems (UAS) has many advantages in the fields of SURVAILLANCE and disaster management compared to space-borne observation, manned missions and in situ methods. The reasons include cost effectiveness, operational safety, and mission efficiency. This has in turn underlined the importance of UAS technology and highlighted a growing need in a more robust and efficient unmanned aerial vehicles to serve specific needs in SURVAILLANCE and disaster management. This paper first gives an overview on the framework for SURVAILLANCE particularly in applications of border control and disaster management and lists several phases of SURVAILLANCE and service descriptions. Based on this overview and SURVAILLANCE phases descriptions, we show the areas and services in which UAS can have significant advantage over traditional methods.

Rendez vous with Saturn's rings

1984 ◽  
Vol 75 ◽  
pp. 743-759 ◽  
Author(s):  
Kerry T. Nock
Keyword(s):  
Solar Energy ◽  
Electric Propulsion ◽  
Power Source ◽  
Propulsion System ◽  
Low Thrust ◽  
Ring Plane ◽  
The Earth ◽  
Total Impulse ◽  
Saturn's Rings

ABSTRACTA mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

Structural Studies on Mitotic Spindle Fibres

1978 ◽  
Vol 36 (3) ◽  
pp. 615-626
Author(s):  
J.R. Mcintosh
Keyword(s):  
Chemical Composition ◽  
Mitotic Spindle ◽  
Structural Studies ◽  
Mitotic Apparatus ◽  
Chemical Studies ◽  
Medical Interest ◽  
Spindle Fibres

The mitotic apparatus is a structure of obvious biological and medical interest, but it has proved to be a difficult cellular machine to understand. The chemical composition of the spindle is only slightly elucidated, largely because of the difficulties in preparing useful isolates of the structure. Chemical studies of the mitotic spindle have been reviewed elsewhere (Mcintosh, 1977), and will not be discussed further here. One would think that structural studies on the mitotic apparatus (MA) in situ would be straightforward, but even with this approach there is some disagreement in the results obtained with various methods and by different investigators. In this paper I will review briefly the approaches which have been used in structural studies of the MA, pointing out the strengths and problems of each approach. I will summarize the principal findings of the different methods, and identify what seem to be fruitful avenues for further work.

Electron Probe Analysis of Muscle

1982 ◽  
Vol 40 ◽  
pp. 398-401
Author(s):  
A. V. Somlyo ◽  
H. Shuman ◽  
A. P. Somlyo
Keyword(s):  
Skeletal Muscle ◽  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Resting State ◽  
Binding Sites ◽  
Electron Probe ◽  
Frog Skeletal Muscle ◽  
Electron Probe Analysis ◽  
Probe Analysis

Electron probe analysis of frozen dried cryosections of frog skeletal muscle, rabbit vascular smooth muscle and of isolated, hyperpermeab1 e rabbit cardiac myocytes has been used to determine the composition of the cytoplasm and organelles in the resting state as well as during contraction. The concentration of elements within the organelles reflects the permeabilities of the organelle membranes to the cytoplasmic ions as well as binding sites. The measurements of [Ca] in the sarcoplasmic reticulum (SR) and mitochondria at rest and during contraction, have direct bearing on their role as release and/or storage sites for Ca in situ.

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