Request for Proposal

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Background

The point of the mountain (POM), located at the south end of the Salt Lake valley, is an internationally known hang gliding and paragliding site due to its consistent wind flow. The geography is unique with two large ranges running North-South parallel to each other, with the POM extending perpendicular to these ranges. The site is actually the remnants of the shoreline (a bench) from Lake Bonneville. There are south and north facing sides that are flown almost every day of the year, weather permitting. Because of its consistency, people travel from all over the world to fly and learn the art of foot-launched flight at this site. People have been flying at this site since the 1920's. During the summer months a daily north flow develops in the afternoon across the Salt Lake valley, given stable weather conditions. In the morning the wind is almost always flowing from the south, a result of Utah valley 'draining' into the Salt Lake valley (among other factors).

Over the years a club was formed and members started preserving the site in whatever capacity they needed to (land was owned by the Geneva gravel company). Recently, a huge rush to develop the south end of the Salt Lake valley boomed and new houses quickly began appearing. With this increased urbanization, Draper City worked with a water utility company to develop the Metro Water treatment facility now located just below the north bench. The developers of this facility worked with our local club to arrive at a suitable easement for us to land safely on their property. In fact, Metro water created a landing zone specifically for us, taking into consideration the slope of the terrain and laying out their facility to not obstruct the wind flow upwind from the landing zone. During this same period of time, the flight club was able to secure the launching area as a Regional County Flight Park.

The Current Problem

The site, however, is not completely preserved at the moment. There is a larger parcel of land directly in front (to the North) of the water facility and our landing zone. This land is owned primarily by the Sorensen Group, a very wealthy development company in Utah. Sorenson does not currently have plans to develop this land, however, it is inevitable. The City of Draper is sympathetic to our site's needs, yet also needs to maximize the taxable income generated from more commercial development. If this land is developed with tall building or even medium sized buildings directly in front of the landing zone, the flight park becomes useless for its intended purpose. Current zoning does not allow for buildings taller than 45 feet to exist on this land, but additional amendments to the master zoning plan may yield to larger structures if city planners deem such plans as being appropriate.

Draper City has asked our club to provide a 'wind study' to illustrate the effects of buildings creating dangerous turbulence within our landing zone during north wind flow events. This study will be used to make a sound decision to limit the development of this commercial property, while still maximizing options for the developers. It is Draper City's and our club's opinion that everyone can win from simply understanding how the wind would be effected by development.

Proposed Solution

A solution to our club's concerns is to ensure that our landing zone and ridge lift are not compromised. In order to complete this, we must model the wind in a reasonable and straight forward fashion to yield results which can then be quantified and directly applied to concerns of safety.

Assumptions:

• Hang gliders and paragliders only fly in a window of reasonable wind speeds (0 to 25 MPH).
• The wind direction to test for is within 20 degrees of north in either direction (relatively perpendicular to the ridge). Once the wind flows at greater angles, ridge lift diminishes and cannot support soaring or safe launching.
  
• Wind at the surface will be moving slower than several meters above due to ground friction slowing the flow. This implies that we need to test for winds at 30? meters aloft as being the test speed.
• 30 foot buildings (rows of town homes) already exist very close to the lower ridge to the East of our launch. General pilot consensus is that this has not impacted the safety of flying directly downwind. (This would, however, impact landing among the structures).
• There are always infinite scenarios when conditions change abruptly due to local meteo events (downdrafts, gust fronts, etc.) that should not be considered for measurement within these tests. It is assumed that the pilot understands general safe conditions.
  

Questions:

• How do we quantify turbulence to safety?
  
• What does the north side realistically look like right now (a baseline)?
• How many model runs and under what scenarios should we execute?
• Does a three dimensional model yield anything more than a two dimensional model, considering the intended audience?
  
• What are the variables we need to consider? (Wind speed, wind direction, flux states, instability, distance from objects to landing zone, height and shape of objects directly upwind from landing zone, natural topography and elevation profile of the domain/site).
• In the case of very large buildings (even if they do not obstruct the landing zone), do we care about how they may impact the lower and upper ridges downwind? Will the turbulence diminish the ridge lift or compromise safety?
  

The Crux

The details of the concerns we hold are ambiguous and, unfortunately, entirely hypothetical as to the development of the land in question. Hence, we are faced with doing a study with few causal elements. Due to these limitations, we have to approach this problem in terms of 'threshold.' More specifically our main question is this:

Given known attributes to the variables listed above, what effects would a building of XYZ dimensions have on the landing zone and the ridges we fly on directly down wind?

Proposed Scenarios to Model

Scenario 1.
Objective: Generate a 2D baseline of the site by modeling how the wind currently flows around the landing zone.

• Wind: 15 mph at 1500 MSL (above significant ground friction) or about 6.7 meters per second.
  
• Direction: 345 degrees
• Domain: Length (X axis) about  700 meters, height (Y axis) about 1440 meters to 1800 meters (MSL). Line starts on north boundary of Sorenson property and ends at top of Steep Mountain.
• Resolution: Around 1 meter.

Scenario 2.
Objective: Test the effects a single block building has on the wind above the landing zone. Use same parameters as scenario 1 and add the following.

• Block building 45 feet high, 100 feet wide and 100 feet long.
  
• Building anchored on south side of Sorenson property directly upwind from landing zone (roughly  150 to 200 meters away).
• Measure a vertical profile of turbulence from center of landing zone.
• Measure a vertical profile of turbulence from 50 meters south of landing zone on lower ridge.

Scenario 3.
Same as scenario 1 except increase the domain to include another dimension to account for larger surface area of topography.

Scenario 4.
Combine elements of scenario 2 and scenario 3, with the following modifications:

• Building dimensions are 45 feet high, 100 feet wide and 80 feet long.

Scenario 5.
Same as scenario 4 with these modifications:

• Building dimensions are 30 feet high, 300 feet wide and 300 feet long.

Resources:

Satellite Aerial view of north side:
http://virtualearth.msn.com/default.aspx?cp=40.47623|-111.896442&style=h&lvl=15&v=1