FR2754600A1 - Demonstration of Coriolis effect - Google Patents

Abstract

The Coriolis effect may be demonstrated either in the form of a model which is observed from the outside or as a full scale presentation which may be entered by persons to make direct observations. The model has a rotating element (1) driven (42) on bearings (43,44) and shaped as a paraboloid. An accelerometer (2) may be moved over the surface of the rotating element (1) by a telescopic arm (47) counterweighted (49) and driven by servomotors (3). A camera (4) enables an operator to observe the accelerometer readings. The full scale presentation uses a rotating lift/capsule to enable persong to enter the rotating paraboloid surface and read an accelerometer trolley directly.

Description

 The present invention relates to a rotary device, didactic and incidentally fun, making it possible to highlight and measure the apparent acceleration resulting from the combination of movements and usually called Coriolis acceleration. Two versions are proposed, one on a large scale where the observer enters the device, measures and observes in situ the effects of Coriolis acceleration, another on a small scale where the observer is outside the device, measures and observe these effects using a camera and an accelerometer which are placed in the device and which rotate with the latter.

 The Coriolis acceleration is easy to expose in a theoretical way, its experimental demonstration is however not easy: the effect is weak except at high angular speed - but then the visual observation is difficult, especially as centrifugal acceleration disturbs this observation.

 The device according to the invention overcomes these difficulties. It comprises, according to a first characteristic, a rotating part of which at least part is in the form of a paraboloid so as to compensate for centrifugal acceleration, as well as an accelerometer which is supported on it and can move on its surface .

 According to particular embodiments - the movements of the accelerometer can be generated by remotely controlled servomotors.

- a nacelle, movable in translation along the axis of the device and being able to be rotated, can make it possible to introduce an observer inside the device itself, by passing it from one level to another regardless of the speeds of relative rotation.

- a camera can be installed inside the rotating part of the device in order to transmit the accelerometer indications outside, in real or delayed time.

 The invention will be better understood, and other objects, details and advantages thereof will appear more clearly in the light of the explanatory description which follows, given solely by way of example and made with reference to the accompanying non-limiting drawings. , in which - Figure 1 shows, in section, the small-scale version of the device according to the invention.

- Figure 2 shows, in section, the large-scale version of the device according to the invention.

- Figure 3 shows, in section, the rotating dish which equips the device.

- Figure 4 is a perspective and sectional representation of a variant of Figure 3 with a double paraboloid, designed for two speeds of rotation wo and w'o.

- Figure 5 shows another variant of Figure 3, in perspective and in section, with a flat part and a paraboloid-shaped part.

FIG. 6 describes in top view an example of grid which can usefully appear, with various colors, on the surface of the rotating parts represented in FIGS. 3, 4 or 5.

- Figure 7 shows, in front view, a pendulum type accelerometer.

- Figure 8 shows, in top view, a ball accelerometer held by springs.

- Figure 9 shows, in front and top views, an accelerometer consisting of two weights held by two flexible orthogonal blades.

- Figure 10 shows schematically as an example 3 possibilities of rotation of the observer during its introduction into the rotating part of the device (evolution of the rotation speed as a function of time).

- Figure 11, in front and top sections, shows a possible embodiment of the observer introduction device.

- Figure 12 shows in section another possible embodiment of this same device.

- Figure 13 is a schematic perspective view of an accelerometer support carriage.

 Before describing in detail the two versions of the device, it is necessary to describe two elements common to these two versions, the paraboloid and the accelerometer.

 In accordance with FIG. 3, the paraboloid (1) has its vertical axis, the opening directed upwards. It is defined so that, when the angular velocity reaches its reference value wO, the vector result R of the centrifugal acceleration C and the acceleration of gravity P is at any point normal to its surface. In practice, the surface may differ slightly from the perfect paraboloid, so that it is the active part of the accelerometer described below which happens to be itself on a perfect paraboloid later, the term paraboloid will integrate this possibility offset. A part of the paraboloid can be replaced by a part of a paraboloid calculated for an angular speed w'0 different from wO, according to FIG. 4, or by a planar sector according to FIG. 5.

To facilitate location, the paraboloid and the possible flat sector may include circular, radial and grid colored bands, as shown by way of example in FIG. 6 in top view.

 The accelerometer (s) (2) can be produced in different ways, without its design influencing the present invention. It must measure acceleration along two orthogonal axes, either directly or by combining two accelerometers on one axis. The reading should preferably be visual for better understanding by the observer, but it can be supplemented by an electric or electronic measurement possibly transmitted remotely and / or recorded on any medium. A viscous fluid can usefully dampen the oscillations of the moving mass. The following three embodiments are given as examples - a pendulum (6), preferably in a cone or a pyramid (7) with a graduated bottom, transparent, according to FIG. 7 in front view.

- a ball (8) held by four springs (9), in a housing (10) graduated and transparent according to Figure 8 in top view.

- Two masses (11) fixed to two flexible rods (12) orthogonal in a graduated housing (13), according to Figure 9 in front and top views.

 In its basic configuration, the large-scale device is produced according to FIG. 2.

Its dimensioning is, for information, of the following order of magnitude - diameter 10 m.

- height 10 m.

- angular speed 1 rad / s.

 It consists of all or part of the following elements - a building (21), which can be totally or partially buried, and which has a fixed ceiling (22).

- a drive system (23), typically electric or electro-hydraulic.

- a lower bearing (24).

- An upper bearing (25) of large diameter, providing a large passage along the axis.

- the dish (1) driven in rotation by the drive system (23).

- an optional flat plate (26), linked to the paraboloid (1) and rotating with it.

in variants, the device may comprise two superimposed paraboloids and calculated for two angular speeds wo and w'o, or else sectors of these paraboloids according to FIG. 4, or else a flat sector and a paraboloidal sector according to FIG. 5.

- a rotating false ceiling (27) intended to mask the fixed ceiling (22).

- A cylindrical part (28), which may include semi-reflecting panels allowing, depending on the lighting conditions, to make the rotation apparent or not.

- a rotary elevator device intended to introduce the observers (29) into the rotating part of the main device, along its axis and from above. A cylindrical nacelle (30) can pass through the upper bearing (25); it is moved vertically and in rotation by a drive mechanism (31). Its rotation up to the speeds of rotation wo or wo may be regular or irregular, according to one or other of the curves given for information in FIG. 10. The nacelle (30) may be crossed by a rod ( 33) for example with square or crenellated section, fixed vertically and rotating the nacelle, according to Figure 1 1; in this case the vertical movements can be controlled by a cable (34). In order to leave the surface of the dish entirely free, another embodiment according to FIG. 12 consists in suspending the nacelle (30) from the rod (35) which drives it both in rotation and in translation; the rod (35) can be usefully produced using a telescopic device.

- one (or more) accelerometer (2); in order to keep its two axes parallel to the plane tangent to the paraboloid at the point concerned, it can be fixed to a carriage (32) shown diagrammatically in FIG. 13. The carriage (32) can be motorized and remote-controlled so as to follow precise trajectories, defined in advance, and at constant speed in horizontal projection. It may also be equipped with a speed and acceleration measurement system for remote and / or delayed analysis.

- various security systems, including emergency access to the interior of the dish and locks on the elevator door.

- means of communication, for example by radio, between the observer (29) and the operator of the device.

 The operating principle is as follows. The rotating part being at the reference speed wo, the observer (29) is introduced by means of the nacelle (30). Using the accelerometer (2), it performs static and then dynamic tests; it can therefore follow the lines drawn on the ground. The use of the carriage (32) may usefully facilitate movements at uniform speed in the horizontal plane. In addition, the effects of Coriolis acceleration can be highlighted in a non-quantitative but spectacular way: rapid movements of the arms, long jumps, throwing ball, use of a bicycle ...

 In its basic configuration, the small-scale device is produced according to FIG. 1.

Its dimensioning is, for information, of the following order of magnitude - diameter 2 m.

- height 1.5 m.

- angular speed 3 rad / s.

 I1 consists of all or part of the following elements - a housing (41), if possible transparent, including a cover and a safety lock.

- a drive system (42), typically electric, capable of integrating a braking system.

- two bearings, lower (43) and upper (44).

- the dish (1); as a variant, it may comprise a sector in the form of a paraboloid calculated for a speed w′o, or a flat sector, according to FIGS. 4 and 5 respectively; in another variant, the dish can be removable, so that it can be replaced by another dish calculated for speed w'o, or by a flat plate.

- a structure (45), supporting the rotating part; it can typically consist of one or more aluminum frames or by the cylindrical extension of the paraboloid (1), similar to that of the large-scale version.

- a two-axis accelerometer (2), which can be mounted on wheels or on balls to facilitate its movement.

- an articulation equipped with two servomotors (3) intended for the remote control in two directions of the movements of the accelerometer (2).

- a telescopic arm (47) driving the accelerometer (2) while allowing it to remain in contact with the paraboloid (1).

- a camera (4) following the movements of the accelerometer (2) and allowing remote observation of its indications; it is the equivalent of the eye of the beholder of the large-scale version.

- a moving mass (49) intended to maintain dynamic balancing when the camera (4) - telescopic arm (47) - accelerometer (2) assembly moves.

- electrical, radioelectric or optical connections between the rotating and fixed parts of the device.

- a set (50) of control - command - display - measurement, comprising the angular speed control, the control of the movements of the accelerometer (2), the display in real time and possibly the recording of the images supplied by the camera , the possible distance measurement of the acceleration. This assembly can usefully be controlled by computer equipment, making it possible in particular to program strictly constant relative travel speeds.

The operating principle is as follows. The rotating part is set to the reference speed of rotation wo; by means of the camera (4) and possibly telemetry,
The observer external to the device observes the acceleration indicated by the accelerometer (2), first in a static position then when the accelerometer (2) moves in a rectilinear fashion in different directions, with a constant speed projected onto the horizontal plane.

 Large-scale applications of the device concern museums or other popular science and technology organizations, as well as amusement parks focused on the future - displacement in the nacelle can in this case be assimilated to an interplanetary journey. The small-scale system finds its place in educational establishments. higher and high schools; it can be used in class as a demonstration, or in the form of practical work to be carried out by students.

Claims (4)

 1) Device intended to highlight and measure the apparent acceleration resulting from the combination of movements and usually called Coriolis acceleration, characterized in that it comprises a rotating part (1) at least part of which has a close form of a paraboloid, and an accelerometer (2) which rests on this surface in the form of a paraboloid (1) and can move thereon.  2) Device according to claim 1 characterized in that servomotors (3) allow remote control of the movements of the accelerometer (2) on the surface in the form of a paraboloid (1).  3) Device according to claim 1 or claim 2, characterized in that it comprises a nacelle (30) movable vertically along the axis of the device and being able to be rotated around this axis, making it possible to pass people from a first fixed plate (22) or in rotation to a second plate (1) or (26) coaxial with the first and rotating at a different speed.  4) Device according to any one of claims 1 to 3, characterized in that a camera (4) is introduced into the rotating part of the device in order to transmit outside of the latter the indications of the accelerometer (2).