Laserfiche WebLink
<br /> <br />. <br /> <br />. <br /> <br />wavy undular jump will occur rather than a strong vertical jump. However, this <br /> <br /> <br />jump situation will still be objectionable, because it creates a reverse curling jump <br /> <br />which has a higher potential of upsetting boaters. Furthermore, the proposed scheme <br /> <br /> <br />will likely require erosion protection further downstream. <br /> <br />The goal is then to improve both whitewater characteristics and energy dissipation. <br />If a chute type of design is to be utili zed, then the fundamental hydraulic concept to <br />be utilized is called a hydraulic jump at an abrupt drop. We have attached a paper <br />that we have prepared which discusses the principles involved (see Appendix). Recent <br />modeling efforts at CU and CSU, undertaken by our firm, have confirmed this theory. <br />The basic idea is to ori ent the bottom of the spillway horizontally and align it <br />properly with the downstream pool water surfa.ce. A pool is constructed downstream <br />and the chute water jet is at the surface moving downstream. The hydraulic jump <br />then occurs below the surface in reverse fashion to the conventional jump flow <br />pattern. The absolute elevation of the jet must be in proper relation to the tai/water <br />elevation. For a given flow, there is a range where the jump will remain underneath. <br />If the tailwater is too low, the jet dives off the end of the chute, and a conventional <br />surface jump occurs. This condition occurred at 3rd Avenue chute where we did <br />all office calculations and no modeling prior to initial construction and thus field <br />modifications were needed to raise the tail water. If the tailwater is too high, a <br />conventional jump on the face of the chute takes place, although we have not had <br />major problems with this. Tapering the chute (reducing width as one moves <br />downstream) and installing wave deflectors also help to reduce or eliminate undesirable <br />wave forms. <br /> <br />We reviewed a single 4-foot drop (the lower dam under future bed conditions) with <br />a whitewater chute and a 4-foot deep pool in order to get a feeling for the magnitude <br />of key hydraulic parameters. Table II presents some of this data (see at-location <br />sketch below). <br /> <br />- <br /> <br />;;!j .=:.1 <br /> <br /> <br />D <br /> <br />~ <br /> <br />C=Froude No <br /> <br />( S <br />f,,=:; [ 'E: <br />Chute <br /> <br />=11( <br />Iii <br /> <br />\\ I_I : <br /> <br />~' <br />I, <br />lil\=:\II~== Pool <br /> <br />Location of Points Described in Tobie ]I <br />