|Title of Invention||
STILLING BASIN FOR CIRCULAR OUTLETS FOR DAM CONSTRUCTION
|Abstract||Energy dissipators or stilling basins form an important and integral part of water resources projects. It is necessary to reduce kinetic energy of water to a permissible limit before releasing it to a channel downstream so that the bed and banks remain protected against excessive scour. In the present work, a stilling basin model keeping the basin floor at the invert level of the pipe outlet for inflow Froude number in the range of 1.70 to 5.50 has been proposed. The new energy dissipator is arrived at by conducting systematic experimentation on the stilling basin models with variations in shapes, sizes and locations of the appurtenances like a wedge shaped splitter block, a modified impact wall, row of wedge shaped baffle blocks and end sill. The performance of the newly proposed model for circular pipe outlets is much better as compared with that of prevalent stilling basin model.|
|Full Text||Field of Invention
This invention relates to the development of new stilling basin model for circular outlets by using suitable shapes, sizes and locations of appurtenances.
Background of the invention
The stilling basin for circular outlets without any drop in the floor is quite long and does not work properly under different tail water depths and running time. Moreover, the geometry of the basin is quite complicated. The appurtenances used are not useful as far as sufficient energy dissipation is concerned. Further, the stilling basin was developed long ago when the concept of energy dissipation was not understood clearly as of today. Keeping theses problems in view, attempts are made to evolve new stilling basin model by using wedge shaped blocks as splitter and baffle blocks along with other appurtenances like impact wall and a sloping end sill. Efforts were also made to see the functioning of the model under different running time and under variable tail water depth. Further, attention is also given to see the applicability of the model under different flow conditions in terms of Froude number. The usage of model was also tested in different diameter of the outlet as well to have more practical utility.
Object of invention
The object of the invention is to improve the process of energy dissipation by using new shapes of blocks inside the stilling basin model. Thus several shapes, sizes and locations of appurtenances like wedge shaped blocks, impact wall and end sill were tried and tested by model studies in the stilling basin models.
Summary of invention
The problem of energy dissipation has been overcome by using specially designed wedge shaped blocks inside the stilling basin. The stilling basin model has been developed while
keeping the basin floor at the invert level of the pipe outlet for inflow Froude number range of 1.70 to 5.50. The new stilling basin models are arrived at by way of physical model studies, which are used as energy dissipator in the water resources projects. Finally geometry of the stilling basin model is obtained which is not only efficient but also shorter in length as compared to the prevalent stilling basin model.
Brief description of the accompanying drawing
The drawing (Fig.l) illustrates the specific embodiment of the present invention. The
recommended design of stilling basin model has four appurtenances namely a wedge
shaped splitter block, an impact wall, two staggered row of wedge shaped baffle blocks
and a sloping sill at the end.
Fig. 1 shows the systematic arrangements of the stilling basin model
Fig. l(a) shows the elevation view of the stilling basin model along with four
appurtenances such as a wedge shaped splitter block, an impact wall, two staggered row
of wedge shaped baffle blocks and a sloping end sill at the end.
Fig. 1 (b) shows the plan view of stilling basin model along with flow direction.
Fig. 1 (c) shows the wedge shaped block in elevation, which is used as a splitter block and
a baffle block.
Fig. l(d) shows the wedge shaped block in plan, which is used as a splitter block and a
Detailed description of the invention with reference to drawing
The attached drawing (Fig.l) shows in plan and elevation of the recommended design of stilling basin model for circular pipe outlets of diameter Id, where d is the diameter of the pipe outlet, without any drop in the bed. The water flows along direction as shown 1, strikes the wedge shaped splitter block of size hb/Wb = O.SOd /0.70d (where hb height of the wedge shaped block, Wb is width of the wedge shaped baffle block) placed at a distance of 0.4d from the exit of the outlet, is being spreaded in to the full width of the stilling basin. It helps in the lateral spreading of the three-dimensional concentrated jet of
water into the full width of stilling basin in a very short length. The jet also entrains a part of surrounding fluid after expansion and in doing so it distributes its kinetic energy throughout a greater mass, causing loss of the energy. Further, the jet of water strikes the impact wall of size 1.25d x 2.50d (1.25 d is the size of hood) placed at 2d with a gap at bottom 0.65d marked as 2. After the wedge shaped splitter block which offers very high drag, the flow impinges on the impact wall and is turned upwards and further comes down after striking the hood thereby dissipating energy. A proper size of hood avoids the splashing of water and helps in the energy dissipation. The appropriate gap below the impact wall allows most of the flow to pass underneath, which creates more horizontal shear and assists in the further energy dissipation by means of higher degree of turbulence on the downstream of impact wall. After this the expanded jet of water which is now a sheet of water meets two rows of wedge shaped baffle blocks of size hb/Wb = 0.5d / 0.5d placed at 2.5d and 3.5d in a staggered manner respectively which are marked as 4 and 5. The staggered rows of wedges shaped baffle blocks offer higher drag and produces a large number of sharp discontinuity layers having small grained eddies between the spaces. Thus eddy currents are produced by the shear action and diffusion, which dissipates a considerable amount of flow energy. In the end the flow reaches a sloping end sill of height 0.75d (slope IV: 2H), which is marked as 6. The sloping end sill lifts the flow from bottom of the channel and creates a strong back current in the form of reverse roller at the end of stilling basin. In order to study the working and the performance of the stilling basin model, an erodible bed consisting of sand material up to the top of the end sill is provided which is marked as 7.
The wedge shaped block which is used as splitter block and baffle block has 150° as vertex angle, Fig.l(d) marked as 8 having cutback at 90° angle on both sides to avoid the reattachment of the jet on sided marked as 9, were used for the development of the stilling basin models. The experiments have indicated that wedge-shaped splitter block and baffle blocks offer more drag due to an increase in the wake area behind these blocks. It has been found that a strong roller with vertical axis is formed on either side of the block in the cutback portion, thus causing the jet to diverge away from the block avoiding reattachment.
l.A energy dissipation system comprises of appurtenances namely a wedge shaped splitter block, an impact wall, two-staggered rows of wedge shaped baffle blocks and a sloping end sill at the end as shown in Fig. 1 .
2. The energy dissipation system as claimed in claim no. 1 where in the size of
wedge shaped splitter block is hb/wb = O.SOd /0.70d
3. The energy dissipation system as claimed in claim no 1 where in size of the
impact wall is 1.25d (hood size) and 2.50d (height).
4. The energy dissipation system as claimed in claim no. 1 where two-staggered
rows of wedge shaped baffle blocks are provided at 2.5d and 3.5d. The size of these
blocks are hh/wh= 0.5d / 0.5d.
5. The energy dissipation system as claimed in claim no. 1 where in a sloping end
sill of sill >f height 0.75d (slope IV: 2H) at the end of the basin is used.
6. The energy dissipation system as claimed in claim no. 1 has the length of the
stilling basin model equal to 4.5d without end sill and 6d including end sill.
7. The energy dissipation system as claimed in claim no. 1 where in the width of
the stilling basin model is provided as 6d.
8. The energy dissipation system as claimed in claim no. 1, the spacing between
wedge shaped baffle blocks is 0.5d and on the sides is equal to 0.25d.
9. The energy dissipation system as claimed in claim no.l uses the appurtenances
like a wedge shaped splitter block, an impact wall, two rows of baffle blocks and an end
sill placed at 0.4d, 2d, 2.5d, 3.5d and 4.5d respectively from the exit of the outlet.
10. The energy dissipation system as claimed in claim no. 1 is useful for inflow
Forude no. range 1 .70 to 5.50.
|Indian Patent Application Number||2547/DEL/2005|
|PG Journal Number||01/2008|
|Date of Filing||20-Sep-2005|
|Name of Patentee||DR. ARUN GOEL|
|Applicant Address||DR. ARUN GOEL, ASSISTANT PROFESSOR, CIVIL ENGINEERING DEPARTMENT NATIONAL INSTITUTE OF TECHNOLOGY (DEEMED KURUKSHETRA-136119, HARYANA, INDIA.|
|PCT International Classification Number||E02B 8/06|
|PCT International Application Number||N/A|
|PCT International Filing date|