1 

A survey of ten years of NLR activities on ringwingbody configurations (19561966)


2 

On the calculation of the propeller noise field around aircraft
A method is given for the calculation of the noise field of a propeller. This method is slightly different from that of Garrick and Watkins. It is believed that the differences in the results indicate the order of the inaccuracy due to the approximations inherent in the two methods. The noise field of two propellers is calculated to show these differences. To estimate the influence of the diffraction around a fuselage some numerical results are given for the diffraction of a plane wave around a circular cylindrical fuselage.

[Abstract]

3 

The design of optimum bodyring wing configurations in supersonic flow at zero lift
A survey is given of the results obtained at the NLR with respect to the determination of optimum bodyring wing configurations at zero lift. It is shown that if reliable data are required for practical shapes the use of exact flow theories is essential. The pressure distribution on the optimum configuration considered here is such that the conclusion seems justified that no separation of the boundary layer will take place in an actual application.

[Abstract]

4 

Optimum shape of a body revolution with base drag at supersonic speed
In this report a method is presented to determine optimum shapes of bodies of revolution taking into account the shape dependent part of the base drag. The latter is achieved by using the Chapman assumption that the base pressure coefficient, when correlated with conditions at a suitable point near the base, depends only on the freestream Mach number if the boundary layer is turbulent. The present method enables the determination of quantitative results, which show the known trend that the optimum bodies have their maximum cross section ahead the base area. The drag reductions obtained are the most significant for relatively slender bodies in the lower supersonic Mach number range.

[Abstract]

5 

Potential theorethical sescription of the flow in a jet deflected by a circular cylinder  Coanda effect
The Coanda effect, being an expedient for the application of blowing boundary layer control^, has been investigated by the NLH to gain an insight into the basic principle and the laws by which it is governed, Within the framework of this investigation a potential theory is developed which, at any rate leads to a qualitative prediction of the increase in volume flow from the slot and the force on the deflecting surface and which will be used as a basis for farther theoretical analysis,

[Abstract]

6 

The behaviour of the wave drag coefficient of a certain optimum body in offâ€“design conditions.
In this report the dragcoefficient of an optimum body with a conical nose has been determined. The body was designed for a Mach number of the undisturbed stream equal to 3. It is found that the curve for the drag coefficient shows a definite kink at the design Mach number. The conclusion is reached that a more general approach for designing optimum bodies will lead to lower values of the wave drag than those obtained by applying current theories.

[Abstract]

7 

On the determination of optium shapes with finite nose angles
This report presents a method for the determination of axiallysymmetric shapes with a given base area that are optimum with respect to wave drag in supersonic flow and which have finite nose angles. Use has been made of the exact nonlinear differential equations for supersonic flow together with the shock equations. The computed results indicate that the optimum bodies with a finite nose angle have a lower drag than those with cusped noses. This would make their practical application of a certain significance. A number of such shapes have been presented in this report.

[Abstract]

8 

On the applicability of a new version of lifting surface theory to nonslender and kinked wings
Results are presented which are obtained by a new elaborate method developed at NLR for the determination of the characteristics of thin wings in subsonic flow.
Attention is paid to the rate of convergence of the numerical solutions, especially with respect to the number of collocation points.
Two rectangular wings have been treated in order to examine the influence of the aspect ratio.
The influence of the rounding of a kink is demonstrated by means of a series of constant choird wings with hyperbolic edges.

[Abstract]

9 

An application of the Nstrip method of integral relations for analyzing the flow around a circular cone
The solution of sets of nonlinear partial differential equations using the method of integral relations is considered. Emphasis is laid on the derivation of a general Nstrip approximation algorithm. In order to check the applicability of this algorithm a program has been written to obtain the solution of the flow field around a circular cone at incidence in supersonic flow. Using the method of Stone, the angle of attck has been taken into account up to the second order. Thus a comparison can be made with the results given by Kopal. The results show that the Nstrip algorithm in the case studied is a very attractive method which leads straightforward to results of high accuracy.

[Abstract]

10 

Beschouwingen over de rol van drukverdelingsberekeningsmethoden bij de vormgeving van vliegtuigvleugels voor hoogsubsone snelheden
In this paper, a discussion is given of some of the aerodynamic difficulties involved in the design of wings for highsubsonic speeds, and of the theoretical methods available to calculate subcritical pressure distributions. It appears that until now only one of these methods, being in fact a semiemperical one, is developed far enough to be of some help in the design stage. The main features of the method are discussed by giving attention to the twodimensional flow problem and by describing the socalled centre solution of an infinite swept wing. The applicability of the method is shown both for two and threedimensional flows by giving comparisons between measured and calculated pressure distributions. Nevertheless the method can not be regarded as a final statement. The development of digital computers in principle has made available for practical application a variety of more general promising approaches to the theoretical solution of subsonic flows around wings. It seems desirable in the authors views to pay full attention to the exploration cf the new possibilities.

[Abstract]

11 

A programme for the construction of a "first characteristic" Flow around a cone with or without inclination
This report gives a programme for the determination of the flow around a circular cone. Both the cases of zeroinclination and of a small inclination have been considered. The programme is written in the international machine language ALGOL and can therefore be operated on any computer having an ALGOL compiler. The purpose of this investigation was mainly to provide an accurate solution for these conical flows in view of their application as initial data along a "first characteristic". These data will enable the determination of the flow field around an axially symmetric configuration having a nose contour which may be considered as conical along a certain distance from the vertex. The programme is discussed in detail and some results obtained by it are included as an example.

[Abstract]

12 

Determination of shapes for minimum drag for a given lift and base area in linearized supersonic flow
This report presents a new method to find shapes that attain minimum wave drag under certain constraints. The constraints considered here are given values for the base area and the lift. The configuration is assumed to be embedded in a volume enclosed by two opposing circular Mach cones, one going through the most forward point of the configuration, the other through the rim of the base. The flow field inside this volume is entirely governed by the perturbation velocities on the Mach cone through the base. In fact, the method deals with the procedure to determine the value of these velocities. Once the velocity distribution along the Mach cone is known the flow field and thus the shape of possible configurations can be found by applying characteristic methods. Two cases are considered; in the first only the value of the base area is prescribed, while in the second also the lift is given. As an example the shape and the axis inclinations of a possible ringwing configuration are calculated. The analysis is based on linearized supersonic flow theory. However, the method can also be adapted to nonlinear flows around shapes with circular crosssections.

[Abstract]

13 

A new approach to the numerical solution of the equation of subsonic lifting surface theory
The present report deals with the numerical treatment of the linearised lifting surface theory through a method which is based upon the representation of the pressure distribution on chordwise direction by a series of Chebyshew polynomials according to Laschka, and upon the determination of the spanwise integral involved by means of trigonometric polynomials such as also appUed by Multhopp. When calculations are performed using Multhopp's method the results show strong variations with increasing number of the spanwise stations and chordwise points, to which the boundary condition is applied. This makes it impossible to obtain a plausible solution. Hence a new method has been developed, where the representation of the pressure distribution in spanwise direction is separated from the representation of the regularised kernel function in spanwise direction. This makes it possible to obtain accurate integrals for a given distribution of pivotal points and leads to results which show a rapid decrease of variation as either the number of spanwise stations or the number df chordwise points or both are increased. This is demonstrated by including a number of results for some wellknown wings. As the method allows of the possibility to take arbitrary positions for the pivotal points, some computations have been performed for different distributions of spanwise stations. The results indicate that further investigations may be useful.

[Abstract]
