= components of (W— WA) in FB or FA = components of Wm FE = velocity of airplane mass centre relative toFA = reference steady value of V = local velocity of the air relative to the Earth = mean value of W, velocity of frame FA = state vector = dX/du, etc., classical stability derivatives = wavelength, 27T/Q, = rms value of stochastic variable indicated by subscript = vector separating two points in FA = angular velocity of airplane relative to FE = local angular velocity of air relative to E = wave number vector in FA = matrix of three-dimensional spectrum functions = matrix of two-dimensional spectrum functions = matrix of one-dimensional spectrum functions = Laplace transform = transpose of matrix = ensemble average = complex conjugate Reference Frames FE:(xE,yE,zE)

Turbulent Wind and Its Effect on Flight

For the 1968 Kansas atmospheric surface-layer experiment, a supplementary analysis is made of the evaluation procedure. Available data on the ratio of wind speeds measured on separate booms show a variation with wind direction which is too large for an open mast. Actually the Kansas mast appears to have carried a bulky array of apparatus at the sonic anemometer levels. It is shown that the air flow interference caused by this obstacle can be satisfactorily estimated by way of potential flow calculations. From these it follows that the sonic anemometer measurements probably have undervalued the free-flow eddy stress by 20% to 30%, which implies that the simultaneous drag plate measurements of stress were generally correct. Also the overestimation of the mean wind speed by the Kansas cup anemometer is found to have been 6% rather than 10%. Some Kansas evaluation results are amended accordingly. The von Karman constant is found to be 0.41 rather than 0.35, and the near-adiabatic eddy diffusivity ratio K

 H
 /K
 M
 becomes 1.0 rather than 1.3. The flux-gradient relations (Businger et al., 1971) after similar revision no longer differ significantly from those obtained elsewhere.

A revaluation of the Kansas mast influence on measurements of stress and cup anemometer overspeeding

Measurements have been made, under neutral conditions, of the turbulent wind structure on a 100m tower at the crest of a hill of height h = 170m. A local velocity maximum, or ‘jet’, was observed at about h/5, below which the ratio of increase in wind speed to the upwind value at the same height was 1.07, and almost independent of height near the surface.



The r.m.s. turbulence components σw σv and σw were also approximately doubled near the surface, but whereas σu and σv both decreased with height, the surface increase in σw extended over the entire height of measurement. Reynolds stress was almost uniform above the ‘jet’, but increased sharply towards the surface, to 3–5 times the upwind value. Departures from neutrality affected the profile shape and the magnitude of turbulence fluctuations very markedly.



Although the size of hill lay outside the range of validity of an analytical theory of Jackson and Hunt, their expressions for velocity and horizontal pressure gradient were in good agreement with the observations. Numerical theories by Frost, Harper and Fichtl and by Taylor, for hills of different shape, but similar slope to the experimental hill, also produced values of surface stress and velocity increase of the magnitude observed.

An experimental study of the profiles of wind speed, shearing stress and turbulence at the crest of a large hill

ATM systems throughout the world are entering a period of major transition and change. The combination of important technological developments and of the globalization of the air transportation industry has necessitated a reexamination of some of the fundamental premises of existing Air Traffic Management (ATM) concepts. New ATM concepts have to be examined, concepts that may place more emphasis on: strategic traffic management; planning and control; partial decentralization of decision-making; and added reliance on the aircraft to carry out strategic ATM plans, with ground controllers confined primarily to a monitoring and supervisory role. 'Free Flight' is a case in point. In order to study, evaluate and validate such new concepts, the ATM community will have to rely heavily on models and computer-based tools/utilities, covering a wide range of issues and metrics related to safety, capacity and efficiency. The state of the art in such modeling support is adequate in some respects, but clearly deficient in others. It is the objective of this study to assist in: (1) assessing the strengths and weaknesses of existing fast-time models and tools for the study of ATM systems and concepts and (2) identifying and prioritizing the requirements for the development of additional modeling capabilities in the near future. A three-stage process has been followed to this purpose: 1. Through the analysis of two case studies involving future ATM system scenarios, as well as through expert assessment, modeling capabilities and supporting tools needed for testing and validating future ATM systems and concepts were identified and described. 2. Existing fast-time ATM models and support tools were reviewed and assessed with regard to the degree to which they offer the capabilities identified under Step 1. 3 . The findings of 1 and 2 were combined to draw conclusions about (1) the best capabilities currently existing, (2) the types of concept testing and validation that can be carried out reliably with such existing capabilities and (3) the currently unavailable modeling capabilities that should receive high priority for near-term research and development. It should be emphasized that the study is concerned only with the class of 'fast time' analytical and simulation models. 'Real time' models, that typically involve humans-in-the-loop, comprise another extensive class which is not addressed in this report. However, the relationship between some of the fast-time models reviewed and a few well-known real-time models is identified in several parts of this report and the potential benefits from the combined use of these two classes of models-a very important subject-are discussed in chapters 4 and 7.

https://rosap.ntl.bts.gov/view/dot/8723/dot_8723_DS1.pdf

Existing and Required Modeling Capabilities for Evaluating ATM Systems and Concepts

Billow turbulence and ocean microstructure

Some potential sources of low-level wind shear in and around airports and their likely effects are probed and analyzed. Wind shear over flat terrain with near-homogeneous surface properties (roughness, specific heat), the turning layer, shear flows over inhomogeneous terrain (airport + urban areas), thunderstorms, turbulent flowfields over bluff bodies (individual buildings), and recirculating wake flow downstream of three-dimensional block bodies are among the topics covered. Overshoot or undershoot of runways, and induced moments (pitch, roll, yaw) in takeoff and landing, and other potential hazards traceable to wind shear patterns at low heights are discussed, with emphasis on mean flow or steady-state wind shear (time-averaged, say 2-min averaged, wind fields). Wind tunnel studies and V/STOL operations are included in the study.

Sources of low-level wind shear around airports

Mathematical models of wind profiles were developed for use in fast time and manned flight simulation studies aimed at defining and eliminating these wind shear hazards. A set of wind profiles and associated wind shear characteristics for stable and neutral boundary layers, thunderstorms, and frontal winds potentially encounterable by aircraft in the terminal area are given. Engineering models of wind shear for direct hazard analysis are presented in mathematical formulae, graphs, tables, and computer lookup routines. The wind profile data utilized to establish the models are described as to location, how obtained, time of observation and number of data points up to 500 m. Recommendations, engineering interpretations and guidelines for use of the data are given and the range of applicability of the wind shear models is described.

/pdf/wind-shear-modeling-for-aircraft-hazard-definition-1drq9ca37i.pdf

Wind shear modeling for aircraft hazard definition

Wind tunnel response tests of cup, vane and propeller wind sensors, determining wind direction and speed parameters, damped and natural frequencies, etc

https://ntrs.nasa.gov/api/citations/19700022611/downloads/19700022611.pdf

Response tests of cup, vane, and propeller wind sensors

Tower influence of wind speed and direction measurements, comparing 150 meter meteorological tower and scale wind tunnel model

Comparison of tower influence on wind velocity for NASA's 150-meter meteorological tower and a wind tunnel model of the tower

At the present time personnel of the NASA Marshall Space Flight Center’s Aerospace Environment Division are engaged in an active program to acquire and analyze high resolution tropospheric and lower stratospheric high resolution wind and temperature profile data. The wind data are acquired by use of the Jimsphere/FPS-16 radar wind sensing system and the temperature data are obtained with a 5 mil bead thermistor mounted onboard the Jimsphere balloon. These systems are capable of resolving perturbations in wind and temperature profiles with vertical wavelengths on the order of 50 meters. The systems are discussed in the paper.

Dennis W. Camp

Papers

Sources of low-level wind shear around airports

Wind shear modeling for aircraft hazard definition

Response tests of cup, vane, and propeller wind sensors

Comparison of tower influence on wind velocity for NASA's 150-meter meteorological tower and a wind tunnel model of the tower

Detailed Wind and Temperature Profiles